Hello @w2vy and welcome to the forum!
There is no clear answer that I know of as to why it happens, but you’ve possibly seen that it seems to be related to rapidly changing files, and that this might be your backup job’s own SQLite database journal file (check Local database path) which is temporary and even less worth backing up than a moving database.
Try –snapshot-policy=on if it fits. It’s most likely to fit if on Windows and not running as a “Standard User”.
This will help in other situations where source files that are then in use would be inaccessible for backup.
If that still has problems, then you could go to screen 3 to add an exclude filter, which might look like this:
/home/tom/.config/Duplicati/CZYBFCCRPU.sqlite* (you can see on its three-dot menu what it did)
Filters gets into the syntax that the Edit as text uses, or you could view the –exclude in Commandline.