This might be the reason then. I think we installed this back in 2018 I dare to say 
It might have been the only type available then? 
The 64-bit installer will detect a 32-bit install and remove it first. You should not have to uninstall the 32-bit version first, but it does not hurt to do so.
WOOHOO… wow, I am beyond impressed here and maybe I overlooked something, but I was indeed able to install 64-bit and it uninstalled 32-bit with ZERO problems. I was able to load up Live TV and can confirm that on 1.29 the pixelation is gone!
So this seems to be a bug in Plex.
Thank you very much to everyone out there for your assistance in tracking this down, along with all the valuable information/context/discussion! It was very helpful and is appreciated. 
EDIT: This post is marked as the “solution” to the bug, which is to install 1.29. However, the bug still persists and is being tracked here:
