Locking Gas Cap Keeps Popping Off

Hi everyone. This might be a silly question, but here goes. I have a 2002 Ford Taurus Wagon, and a couple of years ago I purchased a locking gas cap for it. Every so often, I end up having to add gas when the gas light has come on. Whenever I add gas, I always make sure the cap is on tight and locked. However, once in a while I will open the gas hatch, and the cap is not locked and loose, almost as if it popped off. Other times, it still is locked with no problem. I have no idea why this is happening and what should I do about it. Any help would be appreciated. Thanks.

It’s broken. Get a real one.