[JRTJH]

Are the locks on the bottom of the door or on the side? Most LP tank doors have hinges on the side and if the locks are installed "upside down" they can vibrate loose and allow the door to open. If they are on the bottom, then that may not be what's happening...

If they're on the side, you can turn the lock "upside down" so the key rotates up rather than down and gravity will solve the issue.