In my case, I have crash entries in /var/log/kern.log (you’ll need to copy them via ssh: while being inside my home folder, I used sudo cp -a -p /var/log logcopy/.
My crash logs look like this: Random crashes on DS216+II, DSM 6.2.3, PMS 1.22.3.4392 and earlier - #12 by enchained I wonder if you may have something similar.
Full reinstall is a good idea to try, but just in case, you could also backup your current Plex folder by renaming it. Then, if the same crashes continue even when you set up a small part of your data on the fresh server, you can just go back to your old Plex data and wait for the fix.
I was given these instructions for the fresh install experiment: Random crashes on DS216+II, DSM 6.2.3, PMS 1.22.3.4392 and earlier - #9 by ChuckPa
In case I’ll have to bear crashes for a while, I’m considering to add PMS restart every N hours to the Task Scheduler, or even writing a script that frequently checks if the server stopped to start it.
