If the motor move the slide ok to that point, I certainly wouldn.t think you need a new motor. Does the slide/motor just stop, or does it lug down to a stop?
If it just stops, I'd be tempted to hot wire the motor, see it it completes its travel. If it does, I'd then look for a limit switch, and adjust it. If it lugs to a stop, find out whats stopping it,....like adjustable stops ?? I doubt it has been that way from day 1 ??