[Luke M]

Is everyone else having audio sync issues with this stick?

I'm setting one up for a friend. I've been a long time user of the first and second generation Fire TV's. Not at all impressed with this iteration, so far.

Netflix, Youtube, etc are fine, but nearly every video file I've tried in Kodi has required an audio offset. Typically, that's .05s, but VP9 encodes are more than double that. Nothing I've tried - (FireOS set to Stereo, Kodi set to Stereo, various permutations of frame rate switching) has made any difference whatsoever.
 

I haven't had this problem.

The FireTV 4K does weird things with stereo - it transcodes to DD/DD+. That must add some delay so maybe it's related to your problem (just speculating). You can avoid that by setting Kodi to "fixed" 5.1 instead of "optimized".