Had some shenanigans with my two M.2 drives. They were each setup as their own simple volume.
A couple of months ago I noticed my backup script was showing an error. I logged into the NAS and noticed one of the M.2 volumes had vanished. I checked the storage section and just one M.2. Oh well, i guess it died. Neither drive had been used hard, but they both had a lot of power on time, so meh.
A few weeks ago I get a notification that one of my volumes was corrupt. It didn't give me information on which volume or how it was corrupt. A few days later the remaining M.2 volume vanished. I logged into the NAS and checked the storage section to see the volume had gone, but the drive was still there. Ok, I guess that was the corrupt volume. I create a new simple volume on the M.2 and it's back up and running.
What I didn't notice at the time is this was the drive I thought died a couple of months ago. It's back from the dead, while the drive that was working is now MIA. WTF!
A few days after that I get a notification that there's an update for the NAS' OS. I update and reboot the NAS and the missing drive reappears.
Now both are working fine. ¯\_(ツ)_/¯