Janky vehicle physics with additional mesh sub-components, or doing something wrong?

I am trying to create a vehicle with components that can move and come off (doors, hood, trunk, etc)
I tried adding the meshes as static mesh components to the vehicle as sub-components off the base mesh. This allows the parts to show up, but creates some weird physics issues.

I made a small sample with cubes that are added one at a time with the ‘1’ key, but as each one is added the car breaks and sinks into the floor partly on some wheels.

Using the PhysX Visual Debugger I captured what was happening and it seems the vehicle wheels are not matching up with the wheel locations, and seem to move around as the meshes are added. This doesn’t seem correct.

Am I doing something wrong, or is this some sort of bug?

Link to the PVD file

Link to the project as well, if that helps