central locking issues

[pillgrim1]

have been having issues with central locking on my mk1 fr. the key will manually lock three doors and the boot, the rear offside won't lock. had a locksmith cut a new key today and program it and now both front doors and boot lock but not rear doors.
any thoughts please

 

[mty12345]

Unrelated to the key i'd say. dock lock modules are the main weakness of these cars, along with door seals.

Worth checking where the door wiring passes through into the body.

 

[Alexis27]

Does it make any noise at all? Are you saying it won't lock at all?
Disconnect and reconnecting the battery is probably worth trying.
Likely door module and probably worth getting it changed soon because one day it'll probably decide to flick and deadlock.