OK, try this:
Tell it to move 1"/25.4mm, measure exactly how far it DID move.
Return to 0.000. Does it return to 0.000?
Tell it to move 2"/50.8mm, measure exactly how far it DID move.
Return to 0.000. Does it return to 0.000?
Tell it to move 3"/76.2mm, measure exactly how far it DID move.
Return to 0.000. Does it return to 0.000?
Do each of these 3 times, and report ALL the numbers.
Regards,
Ray L.