Multiple Group Messages in iOS 8

I recently upgraded to iOS 8 after waiting a while in hopes that Apple would fix the basic bugs. Apparently that is not the case. I have a group chat with five of my friends that was working perfectly fine on iOS 7 but is having problems now that I am using iOS 8. The issue is that, despite having the exact same contacts, our group chats are being split into multiple chats. I have tried deleting redundant ones in hopes that they would merge back into one but it appears to not be possible.

All six of the people in the group chat have iPhones and we use iMessage to send our texts. None of us are using Apple IDs; this is done with the phone numbers.

How do I correct this problem? How do I have one thread for the group chat and not have to bounce back and forth just to read texts that are now being thrown out of order?