We have different user reports of similar issues with 15.0
A solution?? Nope, that must be fixed by Apple!!
I've found a workaround using a raspberry Pi, building shairport-sync for airport2 protocol and using it as an airplay receiver... It's not an optimal solution indeed, but is working correctly with audio in sync and no judder, hiccups and out of sync.
I think that the airplay problem is with airplay1 protocol, because if i build shairport-sync for airplay1 i have the same issue.
I was using an airport express 802.11n 1st gen base, and after the upgrade, i've done several test, included a complete reinitialization of apple tv with no luck until this workaround with RPi...
Hoping for a fix very soon.
I think that if multiple of us are sending feedback about the issue, they should prioritize it: Feedback - Apple TV - Apple