I purchased a ps/2 trackball for my mame machine. I connected everything but the trackball has some minor problems. when I move it side to side, the cursor on the screen moves side to side without any problems. when I move either up/down, it's slow and jerky and sometimes doesn't move. it definitely does not move up/down as fast as left/right. anybody seen this problem? do I have a defective trackball? please help