luckeR :
Hello, I am having exactly the same problem.. maybe you have already fixed the problem and can you share how? Thanks a lot.. it drives me crazy already :X (I am not Z370 Gigabyte AORUS Gaming 7)
Same here, guys. It seems that something with a Windows 10 update has caused this to happen (at least in my case), as there haven't been any other changes.
I've also disabled all other input and output devices..but it still plays all sounds through the mic channel (so that when in teamspeak/chat/etc, everyone hears themselves when I have it on continuous transmission..but also hears my in-game or other system sounds, in addition to my voice).
The 'listen to this device' has never been checked, and I made sure to double-check that as well.