This past Sunday, I found this link: documentation/unraid.md at master · binhex/documentation · GitHub.
See question #7 in particular.
I made the recommended changes to my Plex, still under unRaid 6.6.7, and let it run over night. Yesterday morning, it was still running and looking good so I decided to update unRaid to 6.7.0. That was at about 10 in the morning. I’m still running with no database issues, 30 hours later.
This is my Step by Step:
- Go to Docker and stop Plex.
- Go to your appdata folder.
- Rename (or delete) your Plex folder.
- Either reboot now, or update unRaid to 6.7.0 and reboot.
- After the reboot or update, install and configure Plex. Before you click on “APPLY” and after configuring it to your liking, click the “Show more settings…” dropdown near the bottom of the screen. This is where you set your Plex folder location.
- You will see the default setting, /mnt/user/appdata/(container name) . You want to change this to /mnt/cache/appdata/(container name) if you use a cache drive, or to /mnt/disk(number)/appdata/(container name) if you don’t use cache. I don’t use cache, so in my case, I changed /config from /mnt/user/appdata/PlexMediaServer to /mnt/disk1/appdata/PlexMediaServer .
- Now click on “APPLY” to install Plex.
Once you’re satisfied everything is running smoothly, update unRaid from 6.6.7 to 6.7.0, if you didn’t do it in step 4, and everything should keep running smoothly.
Following the above Step by Step, I’ve been up over 30 hours with no errors, longer than it has ever run since initially updating unRaid to 6.7.0 back on May 12th. I hope this helps 
