I doubt a 7.62 round could even damage a 'soft' part of an abbram. The Armor is angled so that the bullet deflects and even .50cal round will just dent the armor at best. The fact that a weak spot might be on the tank is stupid. For the price of the tank I think that every measure would be made to make it as strong as possible. Also, if they know that there's a weak spot on it then they would soon have fixed it.
I think this is just another rumour that has gotten slightly out of hand.