Recently my gas tank door does not lock after fillup. Any advice?

 

had the same problem on my xc70. applied some lubricant on the pin that locks the door and it worked again.

 

recently my gas filler cap won't lock, and was free to swing open at all times. upon closer inspection, a small plastic piece holding the hinge apparatus broke. had to be replaced by dealer under warranty. heard this happens all the time.