15B6: No multichannel audio playback on Media page

Mac OS: only 2 channels of Audio ("Stereo") playback in the Media page. 5.1 surround tracks don't play, only 2 channels totally crazy mixed on 3 output channels. Imported on a timeline in Edit: all is fine, same on Fairlight and Deliver page. Went back to 15Beta5: all ok, must be a new bug in Beta 6.

Mac Pro late 2013, HighSierra 10.13.3

Please solve this item, I do need 5.1 playback on Media page for media selection!

Thanks and best regards

Hans