Intel NUC5i5RYH - No audio over DisplayPort 1.2

Hi,

my NUC is connected to my iiyama B2888UHSU display via the miniDisplayPort-DisplayPort cable which was included with the display.

The display supports DisplayPort version 1.1 and 1.2, it can be changed in the osd menu.

Using DisplayPort 1.1, audio works as expected.

But using DisplayPort 1.2, it won't work. Windows shows everything as usual, the display is set as standard audio device, I can play test tones, but no audio comes out of the display.

Tested on Windows 8.1 Pro x64 with all drivers installed.

Then upgraded to Windows 10 Pro x64, still not working.

Any ideas?