Class 08 Plus Vans Help Please

Doing 9T04 carlisle trip workings part 2. When you get the part of coupling up to 4 vans once coupled vans wheels just lock up and i cant move. All hand brakes are released just will not move well it does at like 1mph and you can see the wheels are locked up. Any advice would much appreciated thanks.

 

You might need to change the brake type, I think it should be on the back wall behind the right driver's seat

 

Yes, the vans are vacuum-braked; the 08 defaults to air-braked.

 

Thanks guys ut never occurred to me to check them all good now thank you.