It could be that by parking itself in the best water flow it has altered what made the hammer happy: nems do that.
It's the advantage of being a nem. Just be glad it's found a spot and parked.
Be patient. The hammer is now doing some brainless 'math' that will possibly persuade it that its best axis of division to get the better flow for itself may be different than previously calculated.
Corals have no brains, but they do math pretty well.