MK7 rear doors open by themselves while driving

[OldAndRusty]

A couple of months back I bought a MK7 LWB van conversion. I've had some issues with some of the locks that I was able to resolve, namely replacing the passenger door lock and adjusting the sliding door.
However, now a new issue has popped up.
When I'm driving (over perhaps a bumpy road), at some point the rear door locks at the top and bottom open up. The only thing holding the doors together is the lock between them that still stays fully locked.
So the doors sway outwards a little and are no longer firm in place.

This happens even when deadlocked and the top and bottom locks are fully open after this.
Even though the van is rather dented and such this doesn't seem mechanical to me, but if it is electrical I have no clue how to fix this.
Any suggestions about what this could be and how to fix it?

[knobby1]

Obviously the top and bottom latches aren't working properly.

Lord Knobrot

[OldAndRusty]

Would replacing the latches be a solution then?
As in, they all 3 open at the same time, or remain all closed. To me that doesn't seem like the problem is with the latches itself right?
Or is there a way for one latch to open another somehow?

[fisjon]

This reminds me of 1969 when I was working for a Vauxhall dealer delivering parts out to garages.
They gave one of the newly introduced Bedford CF vans, on the first trip I was going around a long sweeping curve and the back doors just flew open. luckily none of the parts boxes made an exit.
I assumed that I had not closed them correctly, shut them and carried on. The next day, same bend, clang! doors wide open. So when I got back to the garage I reported it in. Very soon after all the vans were recalled and they were fitted with a longer rod on the top and bottom of the the securing door.
Your van probably has 'stretched' a little top to bottom over the years and maybe the rods are not going far enough into the locating holes and a popping out on the bumps.

[knobby1]

Would replacing the latches be a solution then?
As in, they all 3 open at the same time, or remain all closed. To me that doesn't seem like the problem is with the latches itself right?
Or is there a way for one latch to open another somehow?

I suspect the van is "twisting" somewhat when going around corners....tends to pop the doors open.

Lord Knobrot