trunk lock acting up

[gsfent]

The trunk lock on my 94 Cab is acting up. It will lock when you otherwise 
lock the car with the central locking, but will not unlock unless you put 
the key in the trunk lock. I am getting  a fault code, preventing my 
convertible top from opening. The fault code was cleared, but no help. 
Anything to look for on the trunk lock that would allow it to lock with 
central locking but not unlock? Thx
Regards,
Jerry
91 200qa
94 Cab