It would be interesting to see if the anti-theft alarm will work when this happens. Ultimately it sounds like it needs a new trunk latch assembly, I believe this is seperate from the lock cylinder. If the rotary part of the latch isn't turning far enough, it sounds like the latch itself is at fault. The vacuum element is only for locking and unlocking, shouldn't affect the rotary part. Maybe Donnie has an idea.
I will try to look up and see if I can get a more positive answer.