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.