OK, You need to bypass the the breakout board on the forth axis. It sounds to my there maybe something wrong with the board. I would try to connect the forth axis directly bypassing the breakout board. Leave the other three axis going through the breakout board. It is very very very difficult the isolate a noise problem. First thing you need to do is to be sure its not one of your components (breakout board, driver, cable, motor, etc,) Of course the obvious unshelled power cable running near your control wiring can be something to think about also, but your system worked fine with three axis. I say check the board.