I have spoken to a representative and told them about what thought was an arm problem which was explained to me by my son. Turns out when he sent pictures it's the back side piece that will no stay on. He thinks it's a defect because he said the other is wobly but stays on. He says the other side will not latch in at all. Sorry for all the misunderstanding.  Photos below. BTW..this s not oversized as written.