Hello , could you help me with these , I am not sure about these jumpers you refer to as the cables can go only 1 way?Check the jumpers on the amplifier. Compare the placement of them on the X and Y amplifiers. We had an issue with a machine jumping and making vibrations while the Y-axis was moving. Initially we thought bearings and ballscrews too, turns out two of the jumpers were in the wrong orientation and it wasn't set for the number of pulses the encoder uses. It was reading for more pulses than were actually being generated. If you send the amplifier out, they won't find anything because, it is working the way its designed to, just not the way it is supposed to with your specific machine.