I believe that a alarm 7 indicates a open wire. Since this is the X axis. That would make sense. There are 3 cables going to the motor which moves with the saddle thus flexing in that wireway and prone to hardening from oil and coolant and the cable breaking.
There is a encoder cable, but my concern is for the armature cable and motor tach cable. There screw into the motor side.
The X and Y motors and drives are identical. So those can be swapped for diagnostic purposes (one at a time). Mark the optimization cards with a Sharpie as those stay with their intended axis.