When unlocking the car with the remote, all locks are usually unlocked, but sometimes the rear tailgate stays locked (but I don't notice it remains so). On those occasions, when I later try to lock the car with the remote, it does not work and I have to lock the car manually with the key. It seems the reason the remote does not lock the car normally at those times is because the rear tailgate is already locked -- manually unlocking the tailgate seems to return the normal full-locking function of the remote.

I'm guessing my problem is that the tailgate lock mechanism is occasionally sticking. Am I on the right track? Are the power locks opened/closed with magnets? If so, how do I loosen-up the tailgate lock so it doesn't stick so that my remote becomes more reliable?