Scanning photos does not work at all (0.1.8)

In the hope to end my photo scanning woes and to be up to date, I raised my Nextcloud to 20.0.0 and with that Maps to 0.1.8.

Then I

• cleared my file-cache
• and scanned it again. (not without pruning the file tree a bit - getting rid of obsolete files) occ:files:scan
• then run occ maps:scan-photos beccon

There are around 300.000 files in my tree mainly consists of two SMB/CIFS external shares of which one is of particular interest as it contains all my images uploaded from the phone - so they all contain geotags. Both filescan and scan-photos result in the file trees get traversed - the photo scan shows that it has read quite a few entries.

But nothing appears in the app. Why?

Further analysis shows:
select count(*) from oc_maps_photos where user_id='beccon' -> 191 (which is a tiny fraction)

select count(*) from oc_maps_photos where user_id='beccon' and lat is not null; -> at least they should appear

There is no discrepancy between the filecache and the photo cache anymore:
select count(*) from oc_filecache fc join oc_maps_photos mp on mp.file_id=fc.fileid where mp.user_id='beccon'; -> 191

and it shows my four geotagged images which my UI denies showing
select count(*) from oc_filecache fc join oc_maps_photos mp on mp.file_id=fc.fileid where mp.user_id='beccon' and mp.lat is not null; ->4

Start by reproducing the report with occ:files:scan and occ maps:scan-photos for a user whose photos are on an SMB/CIFS external share. Inspect the oc_maps_photos rows produced for geotagged files and compare them with the app's map display; done means those photos are scanned and appear in the Maps UI.