If you have the time/bandwidth I’d suggest doing a full backup test as described here:
This will essentially download ALL your remote files and make sure they are decryptable and uncompressable. If that comes back with no errors, then we know what’s up there now is good.
If at some point in the future you get these errors again and they are for files that were created before above test process, then we can be pretty sure the issue happened AFTER Duplicati put it on the Destination. So either a problem at the destination or during the download caused the corrupted.
At least in theory.
@kenkendk or @Pectojin , how hard would it be to add “last verified date” to remote file warnings (like the “Verified with size…” ones in the original post)?