Laggy Plex playback

Playback gets choppy, jumping a couple of frames after watching about 1-1.5 hours of a movie. At first it's just one or two frames, then it gets worse and more frequent with a completely frozen playback and unresponsive UI a few minutes after. A device reboot solves the issue, but it comes back after a similar timeframe.

Device: ccwgtv.

Plex: latest and greatest, both on client and server side. Server runs on a NAS.

Stock launcher is disabled using Launcher Manager.