Once installing the latest beta on my 4K, I get huge stuttering in AT&T TV Now when broadcasting audio to my AirServer speakers. This was not a problem prior to installing the latest beta (I was on the prior beta previously). Also no stutter if I set it to play audio through HDMI (but I have no speakers connected via the HDMI signal. Forcing 5.1 or Stereo does not help. Connecting to both regular and lossless AirServer does not make a difference. If I use the remote to pop up any menu (info from top or timeline from bottom) the video is temporarily back to normal speed. On one of my other Apple TV 4Ks I have the beta also installed, but with speakers connected via HDMI. No stutter.
It could be an issue with AT&T TV Now itself, but as stated it was not a problem prior and I have not had any updates to AT&T TV Now.
Vudu streaming doesn't have the issue.