Sometimes people move around at the last second and that can confuse things. But, ya, I've noticed some bugginess with the formations too. I'll look into it.

I didn't engineer the back-end, that was all @steadicat, but the way I think it works is if 3 or more clients confirm a formation they're a part of as correct, it's marked as correct. That way the server doesn't have to check every pixel on the board. But it can cause some issues if some of the clients are laggy.