New backup problem?

Because I was inadvertently backing up a long corrupted library, I decided to delete all my backups and start fresh.

Today, I ran into this problem on a backup destination on a Mini that was working.

image

This -

or this -

both result in this -

Selecting the Clean/Restore option -

Also results in this -

The other backup locations listed here are OK -

There’s plenty of space on that drive -

And the backup folder still being Shared -
image

Thoughts, please.