Servo humming

[TRUCKMAKER]

With out more info on how its set up, the first thing that I would check is the servo end point adjustment. It sounds like the servo is still try to move after the tailgate lock has stopped either opened or closed. The servo has to stop at the same point as your lock linkage in both directions or you'll burn the servo out. Hope that makes sense. I'd start there if that doesn't resolve it try a different servo.