2001 mk6 central locking issue

[aus_transitcamper]

Hey guys, joined up a few days ago and scanned nearly every single thread to try and find someone with a similar issue but, no luck unfortunately.

10/01 transit mk6 2.4 diesel 5 speed ASM
I have been trying to diagnose an issue I’m having with my central locking system.
Firstly when I bought the vehicle it did not come with a keyfob of any kind. Just standard key with blue chip on the back.
Did some googling and found it’s not hard to program a keyfob for the mk6, just ignition on and off 8 times. Purchased 2 fobs off eBay and attempted to code. The vehicle does not go into coding mode at all.
After trying several times with no luck I went to the wreckers, got a second hand module, hooked it up, tried to program fobs and again, not going into learning cycle.

So I thought hey there might be something wrong with the locks themselves.
So after a little more investigating, I noticed that when all doors are closed, (both left and right, sliding and rear)
Sitting in the front seat I can lock the doors via the handle and all 4 doors lock as they should. When I unlock from the handle only the 2 front doors unlock, both left hand sliding door and rear door do not unlock. If I climb into the cargo area and unlock the rear door from the internal mechanism, only the rear and sliding doors unlock. If I am to lock all doors again and open the sliding door from the inside no doors unlock.

I have removed rear door loom, checked continuity on all wires. Check continuity on all sliding door loom from pillar to front LH plug, checked locking and unlocking circuits on both front doors. All checks have come back good no broken wires or high resistance. Have inspected and tested all fuses including ones under steering column no blown fuses. I have cleaned the contacts on sliding door contact switch

If anyone could please shed some light on why my central locking system won’t go into key fob program mode or as to why only my front two doors unlock and not the rear or sliding door that would be much appreciated!
I’m really starting to pull my gear out over this fault I have been at it for a couple days now.