Same issue here, except that the volumes concerned are not even encrypted… In my case, it happens with a new SanDisk external SSD that I have used very moderately for a few weeks. So it's clearly not a physical device-related issue, it's obviously a software issue connected to APFS. Incidentally, on this SSD, there are three APFS volumes in one container and if I unplug and replug two times or more, one of the two volumes on the three — one being a Time Machine backup, the other a volume with various files — are successively concerned. The volume that is not concerned by the problem is a CCC backup clone. I don't know what you can make of that… It shoud be noted that the issue is not specific to macOS 12, it also happens with 11 and 10.15. And many people in the world using macs and external SSDs have faced the problem, see https://bit.ly/3r92xKV The ball is in Apple's court, they are the only ones who can solve the problem.