I found a quick fix....here...
https://davidroessli.com/logs/2026/0...re-web-server/
This works in my case (Calibre-Web on Synology NAS DS 220+ - Container Manager). I synchronize my Calibre Database from my HardDisk to my NAS. Any time I synchronize it, I have to run the script using ssh to get the issue fixed.
It's a temporary solution until Calibre-Web gets updated accordingly.