There is even a bug report on github with no response from the devs. It seems that they are not able to fix it unfortunately..
It's almost impossible to fix something without being able to reproduce it.
I watch videos on Pi4 every day, and sync is always prefect.
There's something in:
files being played
settings used
AVR or TV
A clean install of LE10 on an sdcard, and playing a standard file would be useful to rule out the first two of these.