In case anyone ends up here, I'm about 75% sure that I solved the issue.
It wasn't my BACKUPPC docker accessing my DATABASES live but when it was accessing my NEXTCLOUD-devoted share while Nextcloud was running that the docker daemon would crash and eventually cause my entire system to freeze up.
I've been backing up this Nextcloud share live for several years now and for some reason some update (either w/ nextcloud, docker, or unraid) suddenly caused this to no longer be possible. I still have to figure out how to backup that share, for now I've just turned that backup off but I assume I will have to script some temporary shutdown for the nextcloud docker.
I'll give this a few more days to make sure I'm not imagining things and then will mark this as solved.
