I had a similar issue on my 380. The trunk lock would not lock or unlock with the vacum control. To get it unlocked with the key was not impossible but I had to really persuade it. What I had found was the circlip that atched the actuator for them solinoid to the lock tumbler fell off. Just bumping the car would relock the trunk. Drove me knots till I really looked into it. I could unlock the tunk come back 10 minutes later and it would lock on it's own. After I replaced the missing circlip it functions perfect now