I have the same problem and found out that if I tighten the screws so there is no movement of the lock, the key will either not turn or is very hard to turn. I then loosen each screw an 1/8 of a turn at a time and after only one or two times, the lock works properly and the lock is still tight in the door. It does loosen over time, especially with some of the roads we travel, but I just go back to the formula, tighten, loosen 1/8 turn.
Roy Warren