Refer to the Ballscrew Backlash Test procedure that is appropriate for your machine.
Power off and lock out the machine. Remove the necessary covers to access the axis with the problem. Remove the axis motor cover.
Install the coupler-installation tool  on the motor coupling. Turn the ballscrew so you can see the screw  for the motor-coupling clamp.
Remove the motor screws . Loosen the screw  on the motor-coupling clamp. Remove the motor with the motor-coupling assembly. Remove the ballscrew key . Inspect for damage or wear on the key or keyway.
Make sure the flex pack  in the coupler is not damaged. It should be straight, and tightly compressed together.
Note: If the axis motor is disconnected from the ballscrew, the grid offset and the work offset (such as G54) must be reset. Go to Axis Servo Motor - Set Grid Offset Parameter.