A problem I found with my boot was that the mechanism on the boot pull kept slipping off its position, but didn't effect the key fortunately.

Since then I have added a couple of small cable ties to lock the mechanism.

Had to be done as I've got one of the covers that goes between the rear lights so I can only ever use the cable.

Sorry but the key problem never happened to me, just the pull.

At least if you do get it open you'll see where it's slipped and can sort the pull so it won't happen again

Marc