So after several in-game years, I finally find the Marble Bishop head for the marble sculptures set piece. It was the last one needed, so I stuck it on, then we waited a few days for the full moon. While the moon was still in the phase prior to full, we went to the spot to set up. Suddenly the bishop statue is its normal fixed state, looking like a vase. I mine it, get a normal marble and the broken bishop. I think this may be the effect of a rollback, so I go back to the spot where I found the head, and find nothing. The other marble clockworks are in their fixed states, just this one "healed."