All-clear: I still had a backup and now I have my old status again. Sorry for the panic yesterday.
I tried again with emptying the cache.
Unfortunately this did not lead to any improvement for me either.
I´ve refreshed all metadata but still the newer movies show no poster. Just a thumbnail.
Log attached.
Plex Media Server Logs_2020-02-27_07-48-21.zip (1.1 MB)