Mk6 central locking issue

[Davie rogue]

Good evening,

My drivers side door lock stopped working a few nights back so I ordered a new locking mechanism, the full plug and play unit, popped my original barrel back in
Item arrived today and I fitted it straight onto the van. Have never had issues with the central locking, my old one just wouldnt allow the key to travel into the lock position due to a broken internal latch. Since fitting this, it now locks both front doors but then won't unlock the passenger front door, nor will it lock the backdoors at all. However if you leave any one of the doors open front or back and try to lock it it'll attempt to lock for a second then unlock. So theres signal getting through to the back doors as you can hear the mechanism but only when a door is open, does absolutely nothing when the back doors are closed, dont even hear a noise.
Was wondering if anyone has any insight on this, As I have never had an issue with central locking on this van before swapping out the unit.
Much appreciated in advance

Cheers
Davie

Mk6 2004 90bhp lwb hi top