The 2 Schiit Pre's I had both made a horrible racket with every adjustment of the volume knob. They also both got rave reviews and I never read a word about the clicking relays in all of the reviews I read Until I got them home and went looking for what the issue was.
Apparently they were designed that way!!??
I have a Schiit SAGA pre in my bedroom system and it does indeed do this, but I think the clicking in these (2) scenarios are different. Schiit admits that this is by design. Doesn't bother me, but I know it was quite a pain for a few people.
IMHO, again, I really think the MP is defective. I agree that this shouldn't happen with any DAC. MP needs to check this and find a solution.
Good luck with your pursuit.