Mini-Display port audio issue

I’ve purchased a mini-display to HDMI cable recently for my Surface Pro 3, running the latest insider build . Although it handles video perfectly, it is experiencing an audio issue that I cannot resolve.

Audio will only play for 10 minutes, down to 1 second on occasions. When it stops playing, the only way to resolve, temporarily, is to switch audio output to speakers then back again to the display. However, this resolution only lasts for seconds, at best. I have tried uninstall/reinstall the audio device in question; intel display audio; from device manager, removal/reinstallation of audio drivers, and even disabled/re-enabled the Trusted Platform Module in the UEFI.

Any advice on how I could resolve this issue would be appreciated.

Tony