It seems Gravity Flux doesn't work well. In a game, there was 4 champs at 5 spaces of the selected one, and only 2, 1 ally and 1 ennemy. I guess that those who moved blocked the square where the others should have. (Excuse my poor English) Thanks !
I just tried it out and it seems to move everything within the 5 space radius. The only thing I can think of that would have caused what you have reported is if one of the champions was immovable and that blocked an adjacent champion from being moved too.
