Spraying lube into the lock/keyhole doesn't do much at all, you need to open the tailgate and spray onto/behind the latch until it moves smoothly again.
Luckily you may find that if you leave the lock alone for an hour or so, the mechanism moves far enough under its own steam to eventually catch the latch again and give you one more chance to lubricate the lock
No Basset Hounds were harmed during the production of this notice!


