Update: I have tested with every equipment I own, and sometimes the Questyle sounds good again (like the first day).
What I did:
-Switched to different USB outputs
-Tested two DAC
-Swapped out some cables (I am a non believer, but I have gotten som nice in trades etc.)
-Switch power outakes
What had most effect:
-Power outtake. Where I live there is a 220v while the questyle is 230v, I don't think this should matter, but perhaps is does.