I'm using the onboard controls, on the front of the machine. I don't have the software at the moment so just testing it manually.

All motors are getting the same voltage so I assume the power supply is fine. If I switch the x or y feed to z then that motor travels Smoothly without any problems.

On the surface it looks like there is something wrong with the x/y sockets on the control board but it does seem odd. I would have thought if there was a problem with the board then all axis would be effected or just one.