Thanks for your comments! Yeah, that final level was made pretty close to deadline so I didn't get much time to test it. Essentially there are a few too many objects in the same physics layer that can collide with, and influence the physics of, other objects. (and It is exacerbated by the object's movement speeds being faster in that level). That said, it is do-able. If you can snatch a few junk items out of the crowd pretty quickly after the level starts the scope for weird physics to happen is reduced.
I always start out with a file called Template2D as it's just my default blank Unity project I have saved with the folders already set up and ordered the way I like them. Just saves me 5 minutes when I start something new. Forgot to change the exe name :)