Incomplete Arcs

I’d give it better than 50:50 odds that the issue is in the X-axis pulley gear not being properly secured to the stepper motor shaft. Make sure that the grub screw is secured against the flat of the shaft. This may not be immediately apparent without some inspection.
In any case, the issue is almost certainly mechanical. So check all mechanical linkages for sources of backlash, especially focusing on the X-axis stepper gear.