Airplay wont play sound longer than 1 second, except when mirroring my desktop

Hello Support Community,

Running a Macbook Pro i7 Build 13B42 and using a brand new Apple Tv to stream Audio. The macbook pro is wifi and network utility reports 144 mBit/s steady stream. The apple tv is plugged in via ethernet directly to the modem/router. This conection is fine as I use foxtel on demand through the same ethernet cable. All software and firmware is up to date and I have run the troubleshooting list on the apple tv support page.

For some reason, when selecting output source "apple tv" for my audio only, it will stream for less and less time from when I got the apple TV last week. We are down to 1 second, then after 30 seconds or so the airplay request times out and the audio defaults back to my speakers.

HOWEVER what I can't figure out is when display mirroring is turned on, the audio and vision works perfectly. How come I can't airplay just audio without the strem going dead yet when mirroring my desktop I get no dropouts? None. Perfect. It's playing now in fact.

Please Help

~Ben