Freelander 1 Central Locking Unlocking but not locking

Hi

My doors have gradually stopped unlocking with fob as the years have passed, and the final one (driver's door, LHD) stopped unlocking with fob recently, so I have decided to finally do something about it.
The tailgate opens and locks still tho.

What I don't understand is that all doors will still lock with the fob

Surely, if the motor fails it will fail in both polarities?
And since they failed one by one, its not going to be a fuse issue?
And if they lock its not going to be a wiring issue?

However, I know there are two motors in each door, but I thought 'the other one' was for the dead-locking thing - so you can lock annoying children and wives (or husbands etc) inside?

Or does the deadlock motor also unlock the doors?

Since there are 4 doors gone, buying full locks is too expensive for my Scottish genes, so I was going to get replacement motors, and swear at the car whilst trying to get the locks out and especially in, but now am not sure if that is going to fix it

Can anyone answer my questions, please?

Cheers

EDIT: More Info
Tailgate only unlocks on 2nd press (I think normal)
When inside, locking with fob puts all doors deadlocked and unlock press removes deadlock
There is a 'schunk' noise that seems to come from all/most doors when I press unlock on fob, even after deadlock unlocked
When I lock, dash hazards flash and red light flashes quickly for 2 or 3 seconds, then red light flashes slowly
Brand new correct Varta battery in fob - second one to be sure

I can't completely answer your questions, but yes two motors one for locking & one for unlocking, I think the locking one also unlocks the dead lock otherwise how would you get the doors to open once locked, or do you have to unlock each door from inside?

Another point is taking these locks apart is not an easy task, clips break because they have become brittle overtime, it is very invasive and time consuming with not 100% results.

R40 lock but i think FL1 are the same and Mini ones may also fit.
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2

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5

you can see the black marks where the motor as been wearing away slowly over time.