Y-axis slipping causing failed prints My Y-axis on my Monoprice maker select running ramps 1.4 and Marlin makes a thud noise when moving every now and then. I have noticed a 1 to 2 mm shift in the print when this occurs. I tighten the belts and alas no joy. I ordered new bearings which should be coming Monday. I also tried slowing the print down and still get the same result. Anyone have any ideas.

The issue was the X-axis top smooth rod came out. this caused the extruder to bang around and shift on the Y-axis when it shifted forward. thank everyone for their help.