anyone have ANY idea at all what might be causing my unity project to hang?

it's a simple stage port from a game, not too complex. I tried to set up the collision matrix, and it hanged. So i ended the process and tried again without any of the stage elements but vrcworld. that worked. But then when reintroducing those stage elements, it hangs at the control panel.

I found that it was the map stage itself causing it. I figured maybe the mesh colliders I have on it. I removed them all, the stage has NO collision.

It still does it. something about the mesh itself is causing grief. 

What could it be? Not the highest poly map in the world
I even tried making a new project and doing the collision matrix before importing any assets, and nothing. still hangs.