Hi guys!
I was a really happy user in terms of video/audio quality/smoothness when using “Sync Audio to Display” at the same time as “Audio Passtrough”, but this has changed in Kodi 17 to avoid dropping audio packets when both options are selected at the same time, as very well explained in this thread by FernetMenta; so this is not possible now.
I’m aware this could lead to even better quality with the correct setup/options, but for reasons also explained in that thread (Like ATMOS decoding or simply being able to know my setup is working fine just reading the AV display instead of checking all the time), I still prefer to be able to do both things at the same time, without giving up on having a correct A/V sync, and thus avoiding the video glitch every 40″ if not perfectly in sync with the refresh rate.
I was perfectly fine with the old method dropping audio packets, as for me at least, was completely inaudible (on the contrary as the video glitch), But as FernetMenta said, it might be double implementing some better video sync when passtrough is also selected than coming back to this. I’m not the expert here, but I hope this all makes sense 
Thank you!!
Best.