Multiple backup sources and one destination; what can go wrong?

Unless this is something like disaster recovery, people usually use version not .dlist
Either way, I guess either you keep records or maybe look for a restore tree difference.

Did the log report show a lot of “Added” and “Deleted” source files on a drive switch?
Going back to an old drive will probably take some time to reconnect previous blocks.
I’m not sure it’s smart enough to recognize a new file as an old friend that’s returning.
You could look at the “Opened” report to see if it read through all of the returning files.

Database and destination storage space grow. Per-version consistency check slows.
Very long startups for backup with many backups (>2300) #4664