Super Cache: Doesn't work properly with multi-domains multilingual sites and/or redirects

I use the [Polylang](https://wordpress.org/plugins/polylang/) plugin for my multilingual websites, there are usually redirections or different domains involved:
* One of them (site_A) in particular uses different domains for the two languages. That site has 2x 3 pages to preload, but only 2 (out of 6 total) ever get preloaded.
* The other (site_B) redirects (at the server level) HTTP to HTTPS, and then Polylang redirects the front page to the language-specific front page URL depending on the visitor's detected language (ex: `/en/` and `/fr/`. That site has 2x 5 pages to preload, but only 3 ever get preloaded (out of 10 total).

No matter what I do with WP Super Cache's settings, I am unable to make the preload feature work as expected on either of those websites. And I've been trying to figure this out for _months_, so either there is a bug (or multiple bugs in action), or there is something unclear in the UI somewhere.

Even if I set it with all these simultaneous settings:
* A really long global cache expiry time (48 hours) "just to be sure"
* Enable "`Preload mode (garbage collection disabled. Recommended.)`" in the Preload tab,
* Set the preloader to send me an email before and after preloading,
* _and_ hit the manual "Preload cache now" button

...when I get the "Cache Preload Completed" email, in the case of "site A", its contents are:

```
Cleaning up old supercache files.
Scheduling next preload refresh in 600 minutes.
```

In the case of "site B", the email's contents are empty.

When I go to the "Contents" tab and click "Regenerate cache stats", either no new pages have been cached/supercached, or only some of them (yet I made no "exceptions", no pages are set to be ignored), or even some pages seem to have been removed from the caches (as the number goes down), which makes no sense to me because everything in the UI leads me to believe I explicitly told it to never garbage-collect and at least to never expire things newer than 48 hours...

Here are the debug logs for all this weirdness:

# Site A (multi-domains)

As you can see it really doesn't like the multiple domains:

```
16:12:14 980772 /wp-cron.php?doing_wp_cron=1619539934.0217719078063964843750 wp_cache_get_cookies_values: return:
16:12:14 980772 /wp-cron.php?doing_wp_cron=1619539934.0217719078063964843750 In WP Cache Phase 2
16:12:14 980772 /wp-cron.php?doing_wp_cron=1619539934.0217719078063964843750 Setting up WordPress actions
16:12:14 980772 /wp-cron.php?doing_wp_cron=1619539934.0217719078063964843750 Not caching wp-admin requests.
16:12:18 980938 /wp-cron.php?doing_wp_cron=1619539937.2008240222930908203125 wp_cache_get_cookies_values: return:
16:12:18 980938 /wp-cron.php?doing_wp_cron=1619539937.2008240222930908203125 In WP Cache Phase 2
16:12:18 980938 /wp-cron.php?doing_wp_cron=1619539937.2008240222930908203125 Setting up WordPress actions
16:12:18 980938 /wp-cron.php?doing_wp_cron=1619539937.2008240222930908203125 Not caching wp-admin requests.
16:12:45 982324 /robots.txt wpsc_is_caching_user_disabled: false
16:12:45 982324 /robots.txt wp_cache_get_cookies_values: return:
16:12:45 982324 /robots.txt supercache dir: ABSPATH/wp-content/cache/supercache/site_A_domain1/robots.txt/
16:12:45 982324 /robots.txt No Super Cache file found for current URL: ABSPATH/wp-content/cache/supercache/site_A_domain1/robots.txt/index-https.html
16:12:45 982324 /robots.txt wp_cache_get_cookies_values: return:
16:12:45 982324 /robots.txt wp_cache_phase2: No caching to do as user agent rejected.
16:12:46 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 wp_cache_get_cookies_values: return:
16:12:46 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 In WP Cache Phase 2
16:12:46 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 Setting up WordPress actions
16:12:46 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 Not caching wp-admin requests.
16:12:51 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 wp_cron_preload_cache: doing taxonomy preload.
16:12:51 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 wp_cron_preload_cache: got 100 posts from position 0.
16:12:51 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 get_current_url_supercache_dir: WARNING! site_url (https://site_A_domain1) not found in permalink (https://site_A_domain2/contact-us/).
16:12:51 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 get_current_url_supercache_dir: WARNING! SERVER_NAME (site_A_domain1) not found in permalink (https://site_A_domain2/contact-us/).
16:12:51 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 get_current_url_supercache_dir: Removing SERVER_NAME (site_A_domain2) from permalink (https://site_A_domain2/contact-us/). Is the url right?
16:12:51 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 supercache dir: ABSPATH/wp-content/cache/supercache/site_A_domain1/contact-us/
16:12:51 982696 /contact-us/ wpsc_is_caching_user_disabled: false
16:12:51 982696 /contact-us/ wp_cache_get_cookies_values: return:
16:12:51 982696 /contact-us/ supercache dir: ABSPATH/wp-content/cache/supercache/site_A_domain2/contact-us/
16:12:51 982696 /contact-us/ wp_cache_get_cookies_values: return:
16:12:51 982696 /contact-us/ Fetched gzip static page data from supercache file using PHP. File: ABSPATH/wp-content/cache/supercache/site_A_domain2/contact-us/index-https.html.gz
16:12:51 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 wp_cron_preload_cache: fetched https://site_A_domain2/contact-us/
16:12:52 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 get_current_url_supercache_dir: WARNING! site_url (https://site_A_domain1) not found in permalink (https://site_A_domain2/our-expertise/).
16:12:52 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 get_current_url_supercache_dir: WARNING! SERVER_NAME (site_A_domain1) not found in permalink (https://site_A_domain2/our-expertise/).
16:12:52 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 get_current_url_supercache_dir: Removing SERVER_NAME (site_A_domain2) from permalink (https://site_A_domain2/our-expertise/). Is the url right?
16:12:52 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 supercache dir: ABSPATH/wp-content/cache/supercache/site_A_domain1/our-expertise/
16:12:53 982766 /our-expertise/ wpsc_is_caching_user_disabled: false
16:12:53 982766 /our-expertise/ wp_cache_get_cookies_values: return:
16:12:53 982766 /our-expertise/ supercache dir: ABSPATH/wp-content/cache/supercache/site_A_domain2/our-expertise/
16:12:53 982766 /our-expertise/ wp_cache_get_cookies_values: return:
16:12:53 982766 /our-expertise/ Fetched gzip static page data from supercache file using PHP. File: ABSPATH/wp-content/cache/supercache/site_A_domain2/our-expertise/index-https.html.gz
16:12:53 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 wp_cron_preload_cache: fetched https://site_A_domain2/our-expertise/
16:12:54 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 supercache dir: ABSPATH/wp-content/cache/supercache/site_A_domain1/expertise/
16:12:54 982831 /expertise/ wpsc_is_caching_user_disabled: false
16:12:54 982831 /expertise/ wp_cache_get_cookies_values: return:
16:12:54 982831 /expertise/ supercache dir: ABSPATH/wp-content/cache/supercache/site_A_domain1/expertise/
16:12:54 982831 /expertise/ No Super Cache file found for current URL: ABSPATH/wp-content/cache/supercache/site_A_domain1/expertise/index-https.html
16:12:54 982831 /expertise/ wp_cache_get_cookies_values: return:
16:12:54 982831 /expertise/ In WP Cache Phase 2
16:12:54 982831 /expertise/ Setting up WordPress actions
16:12:54 982831 /expertise/ Created output buffer
16:12:54 982831 /expertise/ wp_cache_get_cookies_values: return:
16:12:54 982831 /expertise/ wpcache_do_rebuild: doing rebuild for ABSPATH/wp-content/cache/supercache/site_A_domain1/expertise/
16:12:54 982831 /expertise/ wpcache_do_rebuild: exiting as directory is not a directory: ABSPATH/wp-content/cache/supercache/site_A_domain1/expertise/
16:12:55 982831 /expertise/ wpsc_is_caching_user_disabled: false
16:12:55 982831 /expertise/ Output buffer callback
16:12:55 982831 /expertise/ wp_cache_get_cookies_values: return:
16:12:55 982831 /expertise/ Anonymous user detected. Only creating Supercache file.
16:12:55 982831 /expertise/ wpsc_is_caching_user_disabled: false
16:12:55 982831 /expertise/ wp_cache_get_cookies_values: return:
16:12:55 982831 /expertise/ Gzipping buffer.
16:12:55 982831 /expertise/ Writing non-gzipped buffer to supercache file.
16:12:55 982831 /expertise/ Writing gzipped buffer to supercache file.
16:12:55 982831 /expertise/ Renamed temp supercache file to ABSPATH/wp-content/cache/supercache/site_A_domain1/expertise/index-https.html
16:12:55 982831 /expertise/ Renamed temp supercache gz file to ABSPATH/wp-content/cache/supercache/site_A_domain1/expertise/index-https.html.gz
16:12:55 982831 /expertise/ Writing gzip content headers. Sending buffer to browser
16:12:55 982831 /expertise/ wp_cache_shutdown_callback: collecting meta data.
16:12:55 982831 /expertise/ Did not write meta file: meta-wp-cache-8679d1db0f19298ed2d77f36858c83b2.php
supercacheonly: 1
wp_cache_not_logged_in: 2
new_cache:1
16:12:55 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 wp_cron_preload_cache: fetched https://site_A_domain1/expertise/
16:12:56 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 supercache dir: ABSPATH/wp-content/cache/supercache/site_A_domain1/nous-contacter/
16:12:57 982951 /nous-contacter/ wpsc_is_caching_user_disabled: false
16:12:57 982951 /nous-contacter/ wp_cache_get_cookies_values: return:
16:12:57 982951 /nous-contacter/ supercache dir: ABSPATH/wp-content/cache/supercache/site_A_domain1/nous-contacter/
16:12:57 982951 /nous-contacter/ No Super Cache file found for current URL: ABSPATH/wp-content/cache/supercache/site_A_domain1/nous-contacter/index-https.html
16:12:57 982951 /nous-contacter/ wp_cache_get_cookies_values: return:
16:12:57 982951 /nous-contacter/ In WP Cache Phase 2
16:12:57 982951 /nous-contacter/ Setting up WordPress actions
16:12:57 982951 /nous-contacter/ Created output buffer
16:12:57 982951 /nous-contacter/ wp_cache_get_cookies_values: return:
16:12:57 982951 /nous-contacter/ wpcache_do_rebuild: doing rebuild for ABSPATH/wp-content/cache/supercache/site_A_domain1/nous-contacter/
16:12:57 982951 /nous-contacter/ wpcache_do_rebuild: exiting as directory is not a directory: ABSPATH/wp-content/cache/supercache/site_A_domain1/nous-contacter/
16:12:58 982951 /nous-contacter/ wpsc_is_caching_user_disabled: false
16:12:58 982951 /nous-contacter/ Output buffer callback
16:12:58 982951 /nous-contacter/ wp_cache_get_cookies_values: return:
16:12:58 982951 /nous-contacter/ Anonymous user detected. Only creating Supercache file.
16:12:58 982951 /nous-contacter/ wpsc_is_caching_user_disabled: false
16:12:58 982951 /nous-contacter/ wp_cache_get_cookies_values: return:
16:12:58 982951 /nous-contacter/ Gzipping buffer.
16:12:58 982951 /nous-contacter/ Writing non-gzipped buffer to supercache file.
16:12:58 982951 /nous-contacter/ Writing gzipped buffer to supercache file.
16:12:58 982951 /nous-contacter/ Renamed temp supercache file to ABSPATH/wp-content/cache/supercache/site_A_domain1/nous-contacter/index-https.html
16:12:58 982951 /nous-contacter/ Renamed temp supercache gz file to ABSPATH/wp-content/cache/supercache/site_A_domain1/nous-contacter/index-https.html.gz
16:12:58 982951 /nous-contacter/ Writing gzip content headers. Sending buffer to browser
16:12:58 982951 /nous-contacter/ wp_cache_shutdown_callback: collecting meta data.
16:12:58 982951 /nous-contacter/ Did not write meta file: meta-wp-cache-85719cabdc9b5298f55f4d46bdabe3a0.php
supercacheonly: 1
wp_cache_not_logged_in: 2
new_cache:1
16:12:58 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 wp_cron_preload_cache: fetched https://site_A_domain1/nous-contacter/
16:12:59 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 get_current_url_supercache_dir: WARNING! site_url (https://site_A_domain1) not found in permalink (https://site_A_domain2/).
16:12:59 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 get_current_url_supercache_dir: WARNING! SERVER_NAME (site_A_domain1) not found in permalink (https://site_A_domain2/).
16:12:59 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 get_current_url_supercache_dir: Removing SERVER_NAME (site_A_domain2) from permalink (https://site_A_domain2/). Is the url right?
16:12:59 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 supercache dir: ABSPATH/wp-content/cache/supercache/site_A_domain1/
16:12:59 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 clear_post_supercache: not deleting post_id 18 as it points at homepage: ABSPATH/wp-content/cache/supercache/site_A_domain1/
16:12:59 983117 / wpsc_is_caching_user_disabled: false
16:12:59 983117 / wp_cache_get_cookies_values: return:
16:12:59 983117 / supercache dir: ABSPATH/wp-content/cache/supercache/site_A_domain2/
16:12:59 983117 / wp_cache_get_cookies_values: return:
16:12:59 983117 / Fetched gzip static page data from supercache file using PHP. File: ABSPATH/wp-content/cache/supercache/site_A_domain2/index-https.html.gz
16:12:59 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 wp_cron_preload_cache: fetched https://site_A_domain2/
16:13:00 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 wp_cron_preload_cache: scheduling the next preload in 30 seconds.
16:13:00 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 wpsc_delete_files: deleting ABSPATH/wp-content/cache/supercache/site_A_domain1/
16:13:00 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 wpsc_delete_files: reading files: nous-contacter
16:13:00 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 wpsc_delete_files: reading files: ..
16:13:00 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 wpsc_delete_files: reading files: .
16:13:00 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 wpsc_delete_files: reading files: expertise
16:13:00 982403 /wp-cron.php?doing_wp_cron=1619539966.2105820178985595703125 wpsc_delete_files: remove directory ABSPATH/wp-content/cache/supercache/site_A_domain1/
16:13:54 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 wp_cache_get_cookies_values: return:
16:13:54 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 In WP Cache Phase 2
16:13:54 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 Setting up WordPress actions
16:13:54 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 Not caching wp-admin requests.
16:14:02 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 wp_cron_preload_cache: no more posts to get. Limit (6) reached.
16:14:03 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 wp_cron_preload_cache: no more posts. scheduling next preload in 600 minutes.
16:14:03 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 wp_cron_preload_cache: clean expired cache files older than 36000 seconds.
16:14:03 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 Cleaning expired cache files in ABSPATH/wp-content/cache/
16:14:03 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 Doing GC on supercache dir: ABSPATH/wp-content/cache/supercache
16:14:03 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 gc: could not delete ABSPATH/wp-content/cache/supercache/index.html as it's protected.
16:14:03 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 prune_super_cache: did not delete file: ABSPATH/wp-content/cache/supercache/index.html
16:14:03 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 gc: could not delete ABSPATH/wp-content/cache/supercache/index.html as it's protected.
16:14:03 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 prune_super_cache: did not delete file as it wasn't a directory or file and not forced to delete new file: ABSPATH/wp-content/cache/supercache/site_A_domain2/index-https.html
16:14:03 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 prune_super_cache: did not delete file as it wasn't a directory or file and not forced to delete new file: ABSPATH/wp-content/cache/supercache/site_A_domain2/contact-us/index-https.html
16:14:03 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 prune_super_cache: did not delete file as it wasn't a directory or file and not forced to delete new file: ABSPATH/wp-content/cache/supercache/site_A_domain2/contact-us/index-https.html.gz
16:14:03 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 prune_super_cache: did not delete file as it wasn't a directory or file and not forced to delete new file: ABSPATH/wp-content/cache/supercache/site_A_domain2/our-expertise/index-https.html
16:14:03 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 prune_super_cache: did not delete file as it wasn't a directory or file and not forced to delete new file: ABSPATH/wp-content/cache/supercache/site_A_domain2/our-expertise/index-https.html.gz
16:14:03 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 prune_super_cache: did not delete file as it wasn't a directory or file and not forced to delete new file: ABSPATH/wp-content/cache/supercache/site_A_domain2/index-https.html.gz
16:14:03 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 prune_super_cache: did not delete file as it wasn't a directory or file and not forced to delete new file: ABSPATH/wp-content/cache/supercache/site_A_domain1/nous-contacter/index-https.html
16:14:03 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 prune_super_cache: did not delete file as it wasn't a directory or file and not forced to delete new file: ABSPATH/wp-content/cache/supercache/site_A_domain1/nous-contacter/index-https.html.gz
16:14:03 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 prune_super_cache: did not delete file as it wasn't a directory or file and not forced to delete new file: ABSPATH/wp-content/cache/supercache/site_A_domain1/expertise/index-https.html
16:14:03 985871 /wp-cron.php?doing_wp_cron=1619540034.1527709960937500000000 prune_super_cache: did not delete file as it wasn't a directory or file and not forced to delete new file: ABSPATH/wp-content/cache/supercache/site_A_domain1/expertise/index-https.html.gz
16:16:06 994207 / wpsc_is_caching_user_disabled: false
16:16:06 994207 / wp_cache_get_cookies_values: return:
16:16:06 994207 / supercache dir: ABSPATH/wp-content/cache/supercache/site_A_domain2/
16:16:06 994207 / wp_cache_get_cookies_values: return:
16:16:06 994207 / Fetched gzip static page data from supercache file using PHP. File: ABSPATH/wp-content/cache/supercache/site_A_domain2/index-https.html.gz
16:18:17 1001560 /wp-cron.php?doing_wp_cron=1619540296.9578909873962402343750 wp_cache_get_cookies_values: return:
16:18:17 1001560 /wp-cron.php?doing_wp_cron=1619540296.9578909873962402343750 In WP Cache Phase 2
16:18:17 1001560 /wp-cron.php?doing_wp_cron=1619540296.9578909873962402343750 Setting up WordPress actions
16:18:17 1001560 /wp-cron.php?doing_wp_cron=1619540296.9578909873962402343750 Not caching wp-admin requests.
16:18:17 1001560 /wp-cron.php?doing_wp_cron=1619540296.9578909873962402343750 maybe_stop_gc: GC flag not found. GC will go ahead..
16:18:17 1001560 /wp-cron.php?doing_wp_cron=1619540296.9578909873962402343750 wp_cache_gc_cron: Set GC Flag. (ABSPATH/wp-content/cache/site_A_domain1_wp_cache_gc.txt)
16:18:17 1001560 /wp-cron.php?doing_wp_cron=1619540296.9578909873962402343750 Cache garbage collection.
16:18:17 1001560 /wp-cron.php?doing_wp_cron=1619540296.9578909873962402343750 Cleaning expired cache files in ABSPATH/wp-content/cache/
16:18:17 1001560 /wp-cron.php?doing_wp_cron=1619540296.9578909873962402343750 GC completed. GC flag deleted.
16:18:17 1001560 /wp-cron.php?doing_wp_cron=1619540296.9578909873962402343750 scheduled wp_cache_gc for 10 seconds time.
```

# Site B (redirects to language-specific `/en/` and `/fr/`)

You can see it doesn't seem to like the redirect, and what's even weirder, there's a mention of a `/wp-content/plugins/sid/sidwso.php` file but _no such file exists on the website's filesystem,_ and I couldn't find any trace of a plugin called "sid", I have no idea what this might be referring to...

```
16:04:07 946854 /wp-cron.php?doing_wp_cron=1619539446.9970939159393310546875 wp_cache_get_cookies_values: return:
16:04:07 946854 /wp-cron.php?doing_wp_cron=1619539446.9970939159393310546875 In WP Cache Phase 2
16:04:07 946854 /wp-cron.php?doing_wp_cron=1619539446.9970939159393310546875 Setting up WordPress actions
16:04:07 946854 /wp-cron.php?doing_wp_cron=1619539446.9970939159393310546875 Not caching wp-admin requests.
16:04:10 947045 /wp-cron.php?doing_wp_cron=1619539449.5527510643005371093750 wp_cache_get_cookies_values: return:
16:04:10 947045 /wp-cron.php?doing_wp_cron=1619539449.5527510643005371093750 In WP Cache Phase 2
16:04:10 947045 /wp-cron.php?doing_wp_cron=1619539449.5527510643005371093750 Setting up WordPress actions
16:04:10 947045 /wp-cron.php?doing_wp_cron=1619539449.5527510643005371093750 Not caching wp-admin requests.
16:04:53 950406 /wp-cron.php?doing_wp_cron=1619539492.7857620716094970703125 wp_cache_get_cookies_values: return:
16:04:53 950406 /wp-cron.php?doing_wp_cron=1619539492.7857620716094970703125 In WP Cache Phase 2
16:04:53 950406 /wp-cron.php?doing_wp_cron=1619539492.7857620716094970703125 Setting up WordPress actions
16:04:53 950406 /wp-cron.php?doing_wp_cron=1619539492.7857620716094970703125 Not caching wp-admin requests.
16:04:58 950406 /wp-cron.php?doing_wp_cron=1619539492.7857620716094970703125 wp_cron_preload_cache: doing taxonomy preload.
16:04:58 950406 /wp-cron.php?doing_wp_cron=1619539492.7857620716094970703125 wp_cron_preload_cache: got 100 posts from position 0.
16:04:58 950406 /wp-cron.php?doing_wp_cron=1619539492.7857620716094970703125 supercache dir: ABSPATH/wp-content/cache/supercache/site_B_domain/fr/realisations/
16:04:58 950406 /wp-cron.php?doing_wp_cron=1619539492.7857620716094970703125 wp_cron_preload_cache: cancelling preload. stop_preload.txt found.
16:06:03 956495 /wp-cron.php?doing_wp_cron=1619539562.1281459331512451171875 wp_cache_get_cookies_values: return:
16:06:03 956495 /wp-cron.php?doing_wp_cron=1619539562.1281459331512451171875 In WP Cache Phase 2
16:06:03 956495 /wp-cron.php?doing_wp_cron=1619539562.1281459331512451171875 Setting up WordPress actions
16:06:03 956495 /wp-cron.php?doing_wp_cron=1619539562.1281459331512451171875 Not caching wp-admin requests.
16:06:25 958176 /wp-content/plugins/sid/sidwso.php wpsc_is_caching_user_disabled: false
16:06:25 958176 /wp-content/plugins/sid/sidwso.php wp_cache_get_cookies_values: return:
16:06:25 958176 /wp-content/plugins/sid/sidwso.php supercache dir: ABSPATH/wp-content/cache/supercache/site_B_domain/wp-content/plugins/sid/sidwso.php/
16:06:25 958176 /wp-content/plugins/sid/sidwso.php No Super Cache file found for current URL: ABSPATH/wp-content/cache/supercache/site_B_domain/wp-content/plugins/sid/sidwso.php/index.html
16:06:25 958176 /wp-content/plugins/sid/sidwso.php wp_cache_get_cookies_values: return:
16:06:25 958176 /wp-content/plugins/sid/sidwso.php In WP Cache Phase 2
16:06:25 958176 /wp-content/plugins/sid/sidwso.php Setting up WordPress actions
16:06:25 958176 /wp-content/plugins/sid/sidwso.php Created output buffer
16:06:25 958176 /wp-content/plugins/sid/sidwso.php wp_cache_get_cookies_values: return:
16:06:25 958176 /wp-content/plugins/sid/sidwso.php wpcache_do_rebuild: doing rebuild for ABSPATH/wp-content/cache/supercache/site_B_domain/wp-content/plugins/sid/sidwso.php/
16:06:25 958176 /wp-content/plugins/sid/sidwso.php wpcache_do_rebuild: exiting as directory is not a directory: ABSPATH/wp-content/cache/supercache/site_B_domain/wp-content/plugins/sid/sidwso.php/
16:06:26 958176 /wp-content/plugins/sid/sidwso.php URI rejected. Not Caching
16:06:26 958176 /wp-content/plugins/sid/sidwso.php wp_cache_maybe_dynamic: returned $buffer
16:06:27 958324 /wp-content/plugins/sid/sidwso.php wpsc_is_caching_user_disabled: false
16:06:27 958324 /wp-content/plugins/sid/sidwso.php wp_cache_get_cookies_values: return:
16:06:27 958324 /wp-content/plugins/sid/sidwso.php supercache dir: ABSPATH/wp-content/cache/supercache/site_B_domain/wp-content/plugins/sid/sidwso.php/
16:06:27 958324 /wp-content/plugins/sid/sidwso.php No Super Cache file found for current URL: ABSPATH/wp-content/cache/supercache/site_B_domain/wp-content/plugins/sid/sidwso.php/index-https.html
16:06:27 958324 /wp-content/plugins/sid/sidwso.php wp_cache_get_cookies_values: return:
16:06:27 958324 /wp-content/plugins/sid/sidwso.php In WP Cache Phase 2
16:06:27 958324 /wp-content/plugins/sid/sidwso.php Setting up WordPress actions
16:06:27 958324 /wp-content/plugins/sid/sidwso.php Created output buffer
16:06:27 958324 /wp-content/plugins/sid/sidwso.php wp_cache_get_cookies_values: return:
16:06:27 958324 /wp-content/plugins/sid/sidwso.php wpcache_do_rebuild: doing rebuild for ABSPATH/wp-content/cache/supercache/site_B_domain/wp-content/plugins/sid/sidwso.php/
16:06:27 958324 /wp-content/plugins/sid/sidwso.php wpcache_do_rebuild: exiting as directory is not a directory: ABSPATH/wp-content/cache/supercache/site_B_domain/wp-content/plugins/sid/sidwso.php/
16:06:29 958324 /wp-content/plugins/sid/sidwso.php URI rejected. Not Caching
16:06:29 958324 /wp-content/plugins/sid/sidwso.php wp_cache_maybe_dynamic: returned $buffer
16:13:01 983246 /wp-cron.php?doing_wp_cron=1619539980.9516260623931884765625 wp_cache_get_cookies_values: return:
16:13:01 983246 /wp-cron.php?doing_wp_cron=1619539980.9516260623931884765625 In WP Cache Phase 2
16:13:01 983246 /wp-cron.php?doing_wp_cron=1619539980.9516260623931884765625 Setting up WordPress actions
16:13:01 983246 /wp-cron.php?doing_wp_cron=1619539980.9516260623931884765625 Not caching wp-admin requests.
16:14:15 987268 /wp-cron.php?doing_wp_cron=1619540055.0838370323181152343750 wp_cache_get_cookies_values: return:
16:14:15 987268 /wp-cron.php?doing_wp_cron=1619540055.0838370323181152343750 In WP Cache Phase 2
16:14:15 987268 /wp-cron.php?doing_wp_cron=1619540055.0838370323181152343750 Setting up WordPress actions
16:14:15 987268 /wp-cron.php?doing_wp_cron=1619540055.0838370323181152343750 Not caching wp-admin requests.
16:17:16 998254 /wp-cron.php?doing_wp_cron=1619540235.7969150543212890625000 wp_cache_get_cookies_values: return:
16:17:16 998254 /wp-cron.php?doing_wp_cron=1619540235.7969150543212890625000 In WP Cache Phase 2
16:17:16 998254 /wp-cron.php?doing_wp_cron=1619540235.7969150543212890625000 Setting up WordPress actions
16:17:16 998254 /wp-cron.php?doing_wp_cron=1619540235.7969150543212890625000 Not caching wp-admin requests.
16:17:16 998254 /wp-cron.php?doing_wp_cron=1619540235.7969150543212890625000 maybe_stop_gc: GC flag not found. GC will go ahead..
16:17:16 998254 /wp-cron.php?doing_wp_cron=1619540235.7969150543212890625000 wp_cache_gc_cron: Set GC Flag. (ABSPATH/wp-content/cache/site_B_domain_wp_cache_gc.txt)
16:17:16 998254 /wp-cron.php?doing_wp_cron=1619540235.7969150543212890625000 Cache garbage collection.
16:17:16 998254 /wp-cron.php?doing_wp_cron=1619540235.7969150543212890625000 Cleaning expired cache files in ABSPATH/wp-content/cache/
16:17:16 998254 /wp-cron.php?doing_wp_cron=1619540235.7969150543212890625000 GC completed. GC flag deleted.
16:17:16 998254 /wp-cron.php?doing_wp_cron=1619540235.7969150543212890625000 scheduled wp_cache_gc for 10 seconds time.
16:21:17 1012421 /wp-cron.php?doing_wp_cron=1619540476.1810081005096435546875 wp_cache_get_cookies_values: return:
16:21:17 1012421 /wp-cron.php?doing_wp_cron=1619540476.1810081005096435546875 In WP Cache Phase 2
16:21:17 1012421 /wp-cron.php?doing_wp_cron=1619540476.1810081005096435546875 Setting up WordPress actions
16:21:17 1012421 /wp-cron.php?doing_wp_cron=1619540476.1810081005096435546875 Not caching wp-admin requests.
16:21:18 1012540 / wpsc_is_caching_user_disabled: false
16:21:18 1012540 / wp_cache_get_cookies_values: return:
16:21:18 1012540 / supercache dir: ABSPATH/wp-content/cache/supercache/site_B_domain/
16:21:18 1012540 / No Super Cache file found for current URL: ABSPATH/wp-content/cache/supercache/site_B_domain/index-https.html
16:21:19 1012540 / wp_cache_get_cookies_values: return:
16:21:19 1012540 / In WP Cache Phase 2
16:21:19 1012540 / Setting up WordPress actions
16:21:19 1012540 / Created output buffer
16:21:19 1012540 / wp_cache_get_cookies_values: return:
16:21:19 1012540 / wpcache_do_rebuild: doing rebuild for ABSPATH/wp-content/cache/supercache/site_B_domain/
16:21:19 1012540 / Redirect detected. Caching disabled.
16:21:19 1012540 / wp_cache_maybe_dynamic: returned $buffer
16:21:20 1012670 /en/frontpage/ wpsc_is_caching_user_disabled: false
16:21:20 1012670 /en/frontpage/ wp_cache_get_cookies_values: return:
16:21:20 1012670 /en/frontpage/ supercache dir: ABSPATH/wp-content/cache/supercache/site_B_domain/en/frontpage/
16:21:20 1012670 /en/frontpage/ wp_cache_get_cookies_values: return:
16:21:20 1012670 /en/frontpage/ Fetched gzip static page data from supercache file using PHP. File: ABSPATH/wp-content/cache/supercache/site_B_domain/en/frontpage/index-https.html.gz
```

Start with the preload feature and the logged entry points wp_cron_preload_cache and get_current_url_supercache_dir. Reproduce the cases involving multiple domains, HTTP-to-HTTPS redirects, and Polylang language redirects, then trace the debug output for the URLs that are skipped or mapped incorrectly. Done means all configured multilingual URLs are preloaded consistently without unexpected cache removal.

Written by the indexing model from the issue text.