If you click on the mesh in the playground and select option 2,3 or 4 and choose another colour, as you rotate you can see transparency particularly from above and underneath.
Ah, ok. (I forgot that you could choose what meshes to load)
I see your issue.
I can see the shadows through the car. I don’t want to ping random people, but I wonder if @Vinc3r could help with this.
There might be a few weird things going on, the back of the car is probably better than the front. A while ago I may have accidentally removed some edges and not sure how to put them back, these might be leaving gaps.