My husband and I TiVoed the scene and it seems that what happened was gravity, pure and simple.
What really got me about cry-baby Freddy was that Hera actually caught the brunt of the blow and you didn't hear her whining or certainly not exploding. She simply commented on it in a matter-of-fact way.
Did Freddy really expect the first one through to hold the gate for the others and become the last one through?!?