No collection fanart + poster in Libreelec 11 nightly

Hi

a fresh installation of Libreelec 11 nightly is not showing poster and fanart of film collections.

Other artwork ist loaded/displayed without any issue.

Artwork and movies are stored on a home-server.
Access via smb.
Path to the collection artwork is set in settings.

Was running smooth with previous versions of Libreelec for many years.

Another device, which I simply updated from 10.0.3 to the latest nightly of 11 can display collection poster + fanart without any issue.

Am I missing something out (any misconfiguration from my side)?

Ok, identified the issue, but not the root cause.

All images in my collection-folder were deleted.

Copied back a backup and it's working.

What initially deleted the pics is unclear.

As I have not accessed them in the folder directly since ages, it has to be initiated by some task from libreelec or kodi or ember media manager.