Deadlocking Relays on BSI - C3

[addo]

I'm halfway into this one.

Scenario: Customer driving late at night, pulls to the roadside to answer phone. Presses console locking button for additional peace of mind; car locks. Upon trying to unlock car, central locking clicks but does not release. Solution is to wind down driver's window and unlock door from outside with key - only driver's door has key slot. Once this lock has been turned and the outside handle used to release the doo, the driver's door only can be opened from inside.

Central locking "lock" button can be used any time to re-lock car but neither it nor keyfob will release locks - thus requiring the window-down, lean out approach.

I have the BSI stripped, and can feel the relays clicking when actuating. I'm surmising that one of the relays' contacts has welded itself to its earth lug in the "lock on" phase. This is why it doesn't blow fuses when locking, but also when you go to unlock it won't release the moving contact to touch positive and release the locks.

Am I completely and utterly barking up the wrong tree, or does this sound feasible? Should I buzz out the harness first to check for breaks?

Thanks, Adam.