Generally you can resync by extending it and holding the control for another 3-5 seconds when it reaches its stop. Go back and forth a few times always holding the control until the electronics sense both motors have reached their limit. This lets the other motor pull it in or out and resync.
If that won’t get the motors synced then it probably is a mechanical problem, maybe alignment.
FWIW full length slides are probably beyond the capabilities of the motor/gear mechanism and will fail over time. Vroom is an outfit in Phoenix that offers much sturdier slide mechanisms particularly for full length slides. Read Judge's account of replacing his slide components here:
https://www.thorforums.com/forums/f2...v34-28659.html
David