Train blowing vehicles truck length away when multiple carriages are added. help

[Japll]

Image attached shows how the train is setup and functions perfectly fine going down track etc but the only problem im having is it blowing up any vehicle that it passes, for example the grain wagon you see in red on right hand side blows up that distance away from the train. is there something I'm missing would love some help for this.

Further information
it works fine with just one engine but when multiple vehicles added to train causes vehicles nearby to blow up when passed.
i changed protos of train in image to the base game train that works and i still get the same problem .
i tried turning collision off on the wagons and train but causes the game to crash when starting it.