Unable to update logs with log-analytics

When I try to run /usr/bin/python2 /var/www/matomo/misc/log-analytics/import_logs.py --url=https://example.com --idsite=1 --recorders=4 --enable-http-errors --enable-http-redirects --enable-bots /var/log/containers/nginx/access.ota.log I get the following output :

0 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
Parsing log /var/log/containers/nginx/access.ota.log...
2020-11-11 19:54:44,301: [INFO] Error when connecting to Matomo: HTTP Error 400: Bad Request
2020-11-11 19:54:44,302: [INFO] Retrying request, attempt number 2
2020-11-11 19:54:44,319: [INFO] Error when connecting to Matomo: HTTP Error 400: Bad Request
2020-11-11 19:54:44,320: [INFO] Retrying request, attempt number 2
2020-11-11 19:54:44,322: [INFO] Error when connecting to Matomo: HTTP Error 400: Bad Request
2020-11-11 19:54:44,322: [INFO] Retrying request, attempt number 2
2020-11-11 19:54:44,323: [INFO] Error when connecting to Matomo: HTTP Error 400: Bad Request
2020-11-11 19:54:44,325: [INFO] Retrying request, attempt number 2
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
2020-11-11 19:54:54,362: [INFO] Error when connecting to Matomo: HTTP Error 400: Bad Request
2020-11-11 19:54:54,363: [INFO] Retrying request, attempt number 3
2020-11-11 19:54:54,384: [INFO] Error when connecting to Matomo: HTTP Error 400: Bad Request
2020-11-11 19:54:54,384: [INFO] Retrying request, attempt number 3
2020-11-11 19:54:54,386: [INFO] Error when connecting to Matomo: HTTP Error 400: Bad Request
2020-11-11 19:54:54,386: [INFO] Error when connecting to Matomo: HTTP Error 400: Bad Request
2020-11-11 19:54:54,387: [INFO] Retrying request, attempt number 3
2020-11-11 19:54:54,387: [INFO] Retrying request, attempt number 3
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
3202 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
2020-11-11 19:55:04,412: [INFO] Error when connecting to Matomo: HTTP Error 400: Bad Request
2020-11-11 19:55:04,413: [INFO] Max number of attempts reached, server is unreachable!
Fatal error: Server returned status 400 (Bad Request).
Is the BulkTracking plugin disabled?
You can restart the import of "/var/log/containers/nginx/access.ota.log" from the point it failed by specifying --skip=2 on the command line.

It suddenly stopped working since last one week even though there were no noticeable changes. Any idea what could have gone wrong? BulkTracking in enabled

Start with misc/log-analytics/import_logs.py and the shown command/output; inspect how requests reach Matomo and how HTTP 400 responses are reported. Check the BulkTracking setting and reproduce with the referenced nginx access log; done means the import records lines without the repeated 400 failure.