Update on this. So I did manage to get the fault to repeat in daylight so, my darkness theory was a load of old bollox!
The power latching is done at the rear of the door so it’s down the the adjustment of the striker catch in the C pillar relative to the door when it’s almost closed.
Operate the door from the outside, close the door very gently till it’s almost engaged but not quite.
Push the rear of the door by the latch inwards till you hear the first click. This will activate the cinch motor and close the door.
By doing this a few times you’ll learn just how much force is required to get it to work correctly.
Once inside, place your finger tips in the sliding window track at the rear of the door and pull it inwards till you hear the click.
If it’s still tricky then you may need to loosen and adjust the striker latch on the C pillar. Mark it first with tape before doing this.
I’m beginning to suspect the fault is logged when it has to 3x cinch, so not necessarily a motor fault
but more a maladjustment indicator?

