This was caused by the recent changes made to the way we handle matrix
copies. The matrix copy assumed that the uniform iteration was the same
as creation order. But this was far from true. The reality was that
the iterator was reverse for `unichunk` but not for `unichunk->uniforms`
so this was recreating wrong matrix.
I rewrote this part to always use reverse iteration and fix the
copy destination.
Also I simplified the code making the assumption this won't be used for
anything else than mat4.
ca37654b63