If not if its the same then there is usually a sticking sometimes faulty lock mechanism on the van.
Transit van side door wont lock.
Try opening the rear door driver side and operate the inside handle.
Video about how you can open stuck sliding door on ford transit mk6 van.
All motors work on all doors as can hear them even clear the contact on the side sliding door still does the same locks then unlocks its self deker gough may 2020.
I had to take out the lock to repair and decided to show whats happening when rotary knob gets stuck.
What happens is when it receives the lock signal because one of the locks wont fully lock as above it then kicks the locks open again as the system thinks there is a door not fully closed etc.
Then lock it all up as normal.
If your drivers side door won t open try spraying some wd 40 into the area where the door connects with the lock inside the car.
This happened on a 10 plate transit last year more than once.
This will lubricate the lock.