Volvo 740 Central Locking Problem

[Ednamillion]

Just looking for some fresh eyes on this...

A few weeks back the central locking on my 740 estate failed, no doors nor tailgate locking from the key in the drivers door other than the drivers door itself (mechanical).

Checking the tailgate I noticed that I couldn't lock it with the key so went hunting there for a problem and found a seized motor. Freed that up and now that locks/unlocks from the drivers door but still nothing in the other three doors.

What I think I can determine is that the signal from the drivers door is getting to the central relay (as the relay is clicking, the tailgate is locking/unlocking) and that the relay is functioning (again, as the tailgate is activating).

Each passenger door has a locking motor/solenoid - could the seized tailgate motor have fried the other door actuators? Isn't it strange how they each failed at the same time..?

Any thoughts would be appreciated. Haven't gone multimetering yet.