I have also adjusted the 4 bolts on the gantry and read all the items that matched this in the search box for the forums. I thought it would be the table where the prints sits but that thing is rock solid. I dont print fast. Using Marlin RC7 MPCNC w/LCD firmware with nothing changed. The only oddity I have found is that the Z motor gets quite a bit warmer than the X or Y motors. Doesnt seem to be any binding. The Z was very sloppy at the bottom at first until I tightened the 4 tensioner bolts on the outside of the Gantry. Much more stable now. It made a print of one of those fine. So maybe it slinging that heave head around causes it to get off? just done see how it would do it so consistently.