That turns out to be exactly right. I tried turning ransomware protection on/off, and it has an immediate effect. I.e. "catastrophic failure" versus working correctly.
Sounds like a good way to protect those libraries. Although it doesn't seem to help from other media agents which don't have that library configured, but can still reach. (same VLAN).
I hope to be able to read somewhere about what the ransomware protection does exactly. I'm curious now.
Too bad it doesn't help at all against those other errors. Might be library corruption, but i'm not sure how to arrange shutting down backups for possibly weeks to get it all verified.
Thanks for your help.