Vehicle Collision freak out

Hi, I am making a dump truck and all works fine for the chassis and wheels. But when I come to put the tray on the back as a secondary mesh within the vehicle pawn blueprint it goes crazy and flips all over the place. When I disable all the collision on the tray it goes back to behaving itself.

When I enable ‘showdebug vehicle’ I noticed that the collisions on the chassis change.

This is what it looks like without collision on the tray.

Here is a shot of it mid flight after the collision has been turned on the tray. Notice that the wheel collision has changed.

Here I have lifted the tray so it avoids all the collisions so it doesn’t go crazy. For some reason the chassis collisions have totally changed when I turn on the collision of the tray.

Is there a better way of having a tray able to tip things out on a vehicle? Currently I just have it assigned to tip back and forth with two keys.

Any help will be greatly appreciated.

Thanks, Tocs