I do not see a reason why Plex is stopping.
I did find another thread where several others are experience the same issue.
Please configure Plex Media Server to log its memory usage. Follow the instructions in this post.
This adds memory usage info to some log file entries (ex: Memory Usage: 53.0 MB/2423.0 MB).
If/when Plex stops again, pull the log files and post on the Plex stops running every once in awhile? Why? thread.
Hopefully your logs along with the others will help find the root cause of the problem.
