I'd say there are two things going wrong here.
1) it's a bit unreasonable to generate 32 physics objects on top of the same location and not expect some problems
2) Box2D web seems to definitely have trouble with this, locking the objects at odd locations.
If you switch to Box2D asm.js, as the engine, it actually works better.
(Also you need to get rid of the one object that is already in the layout, to control generating specific numbers.)