This is a newer problem. When I first got everything set up, I did not have this issue. The only thing that changed is my ethernet cable(upgrade) and the plex version(s).
When I use plex and pause a show, most of the time, the audio will play like normal, but the video does not.
The only fix I’ve found for this is to rewind the media 10 seconds so the audio and video sync up.
My connect is via a gigabit ethernet cord.
Plex runs on my NAS(unraid) that contains all of the local content.
If you mean audio sync gets out of wack. It is a known issue the Android team has been trying to figure out. It has been a tricky one unfortunately. Can usually reproduce by skipping ahead.
If you can provide the app logs after it happens I can add it to the bug report. If the developers think it is something else it will get split into another separate report.