I have a similar issue. I am running an nVidia Shield (500GB) running the latest version of PLEX. I have tried two configurations:
Configuration 1: nVidia Shield as a PLEX media server and client. This is where I have the most issues. The PLEX client crashes about once or twice an hour. Scrolling mostly causes it to crash. It also does crash while a show is being played but that is somewhat less frequent.
Configuration 2: An Intel NUC (running Windows 10) as the PLEX media server. In this scenario, the nVidia Shield is run as a PLEX client and the PLEX media server is disabled on the Shield (this is important). This is much more reliable. PLEX still crashes but only once or twice a week. The interface also seems to run faster (better scrolling, etc.). But in this configuration you must disable the PLEX media server component so that it is not running. Only the PLEX client is running. Until I did this the crashes were much more frequent.
Some other config info: Network is 1GbE wired (no WiFi). Synology 8 drive NAS.