>>287325807
>>287326319
>>287325807
Also there's this https://forum.unity.com/threads/odd-physics-behavior-with-stacked-objects.376234/
http://docs.unity3d.com/ScriptReference/Rigidbody-angularDrag.html

Seriously though finding a way to have physics disabled until you draw the tile would be ideal, because it would be more performant friendly.

You already used black magic to have every tile on ONE material and also instanced the mesh so it's a single pass, might as well go all the way