As for Plex I've had way too many issues to list. Networking issues, having to restart the Plex app after the device went to sleep, etc. When I switched to using Plex on the Apple TV all the issues went away.
It should be noted that I have re-pasted and cleaned the dust of my Shield a couple of times since I got it 10 years ago.
Probably one of the big issues here. It's probably still the best Android TV you can get today but that's really sad because the SoC in it came out in 2015 (with some improvements in 2019). It was probably worse than what was in Apple TV at the time and Apple refreshed it two times since then.