Good day. Purchased by 94 E500 back in October, odd issue with vacuum door locks. They will always unlock from trunk or driver's door, but sometimes they do not want to lock. More often I can get them to lock from the trunk, and sometimes I can get them to lock from the driver's door (either with the plunger from inside or with the key outside) but often trying to use the plunger or key leads to just the driver's door locking, without any response from the rest of the system. If I manually lock everything, they will all unlock with the key, so I not think it is an issue with the under rear seat pump. The car does have an aftermarket alarm - not sure if this matters. I am thinking there is something wrong with the driver's door vacuum switch but will appreciate any suggestions.