Really unfortunate that this thread has been around for over a year and no solution by Arturia has been posted yet or at the very least, acknowledged. Now I get to join the club. Turned on the brute in the studio today and discovered I'm having the exact same issue with the filter (only makes sound with the notch selected). Just filed a ticket with support. I'll see where that goes. Hopefully this is an easy fix and not a component gone bad.
Any more info please post.