I have a long-time setup for backups where each computer to be backed up has a particular folder which is mapped onto the backup computer.
Recently, the backups didn't run because, it appears, the mapped drives weren't "there".
But they were and they weren't showing as disconnected.
I opened them in Windows just fine.
After that, the backups would run normally.
I can't have this happening and I can't figure out what was causing this strange behavior. This has been working for years!