Lock Actuator Problem

I had a Valet 562T remote start professionally installed on my daughters 2004 Cavalier (2dr). Later I had power locks (keyless) added by the same installer. The locks worked fine for about a month. That's when we began having problems with the passenger door lock (actuator?). It locked OK but when the unlock button was pushed there was a very loud grinding sound coming from the door and it did not unlock. We returned the car to the installer for a fix. For a few days the lock again worked fine. Then the passenger door locked but would not unlock (the actuator moved, but not enough to unlock the door). Again we returned to the car to the installer. Now the lock works (lock-unlock) but the loud grinding is back on the lock cycle (actuator arm extended). The installer says there's nothing more that can be done...we either live with the noise or the lock won't work. I know little about remote starters, power locks, etc., but this just doesn't seem right. Is there anyone who can give me some idea why this would be happening. Is it a bad actuator (2 wire)? Would replacing the actuator fix the problem? Is the actuator motor running on to long at the end of the arms travel (sounds like gears grinding). Thanks in advance for any help/info.

So, if I understand you correctly...it may be that it's just a bad actuator and replacing it will solve the problem. Actuators aren't that expensive, why wouldn't the installer just replace it? Is there any other reasons (more costly for the installer to fix) this could happen?

Could be several things, bad motor, to much friction in door lock mechanism, improperly mounted door motor, or low 12V current? Most likely is improperly mounted door motor. Axis of the motor should point directly to the lock-link pivot point. The actuator rod can be any shape.Knowledge is Indisputable, Opinions are Subjective.