I'm having this issue also. The only resolution I have at this point is to set the plex Docker template to use the following repository:
plexinc/pms-docker:1.30.2.6563-3d4dc0cce
When I first experienced the crashes I determined that it was right after I had updated Plex. So I disabled the updated Plex docker and crashes went away. And as soon as I enabled Plex, crashes started again. I then rolled back to the version listed above and ran with zero issues. So I've been stuck on that version for awhile now.
Yesterday I decided to try it again and upgrade Plex to the current version. This morning I noticed my server crashed again. So for now I just set the version back to what I was using until I can figure out the issue.