[ubuntu] HDMI stops working on applications

Hi,

My system uses HDMI audio via the optical output on the TV, I am currently using 14.04 LTS and after an upgrade audio stopped working on all apps, youtube, kodi etc. HDMI audio does work on the Left Right test in audio settings and its shown selected, so HDMI audio is not broken as it can work. After ruing the LR test the the DAC shows the HDMI audio link is working as it shows lock, however as soon as an app using audio is started the HDMI audio shuts down as the DAC shows no lock, I saw this on upgrading to 16.04 and I had USB sticks with 14.04 and 16.04 and 16.04 and audio never worked on 16.04, other than the LR test, I went back to 16.04. Any ideas?

edit HW is Intel NUC Intel NUC D34010WYK with corei3 4010U

BR

Russel