Some of the older Philips Android TV with Android v5 have a problem. IIRC the system tells them a wrong set of supported codecs, something like that. Which in turn Plex things it can play AC3 audio on that devices, which doesn’t work. I do started the same item twice: (1st try) The player started, showed me the video and sound for like 1 sec and the item was finished (2nd and onward) the audio plays but the video isn’t shown.
The problem is well known and already existed with several threads in this forum even prior to ExoPlayer 2. Hope you can fix it with the new engine.
TV Model: 32PFK6500
Firmware: QM152E v0.7.40.0