Depends on what the clump was, could be an air hammer. Or if it's that new could've been the drain line rubbing. That's a tough one to diagnose without being there. Sorry for the late response. If it's a hard thunk once the water shut off, water hammer. If not and more of a rubbingish sound probably too small of a hole drilled for the drain line.
Problem solved, learned lesson, if all fixtures make thumping noise, put youre hand in a cartridge and if you feel an abnormal vibration on one, thats the the bad one