Relay sliding door central locking fob vs drivers door

[PeteRelay]

Hi all
The sliding door of our Relay will only lock using the remote key fob (and only on the second press - first clunk = front doors, 2nd clunk = sliding door) - should I be able to lock it with the key in the drivers door as well? It will unlock using the key in the drivers door, but not lock.
Should I start looking for wiring diagrams, metering the loom at the door end, etc?
I have disconnected the cable to the sliding door that detected it was open, as that was the only was I could get it to lock at all. (Mis-fitting door - loads of trouble with it)
Thanks!
Pete

Citroen Relay 2013 2.2 HDI 130