Neither. Use the container field "Version" and change it from "latest" to "public" and it'll pull the last stable release automatically. Plex's release notes say you're safe to downgrade to 1.31.2 or later without messing up your database.
Just did this myself, but still giving it a couple days to see if the problem pops up again. Just moved hardware from an old Xeon system to a new 14700k system with 64GB, and the same stupid problem persisted across hardware. No matter how much RAM is in there, Plex has been filling it up, locking up Unraid entirely (no GUI and no SSH, but CPU churning, fans going crazy)... finally put a RAM limit on the container so it doesn't lock up the server, but it still kills the container. So we'll see if rolling back fixes anything...