It's not a major problem but I'm using iOS 10 PB 7 and I'm in a group chat with the rest being on iOS 9 except one iPhone 4 user on iOS 7. Whenever the iPhone 4 user texts, I don't see his texts on the main group chat, theyre just sent as a new group chat. Why is this happening if they're just normal texts and I'm not even using the new iMessage features?