Yeah, I have the same problem in my del sol's passenger side door. I have no idea what the trouble is - just old locks? Maybe rain got in there and rusted something? for me, it helps if push up on the key as you turn, it goes every time for me that way. Otherwise it "sticks"...like there is some notch it's catching. If you figure out exactly what it is, let me know! But unless it gets worse, I wouldn't call a locksmith or anything.