I started a conversation with someone and when they replied back the message showed up in my Messages app. as a new conversation but I could not open it. Ever time I tried to open the conversation I was taken to the conversation that I had sent out but my friends message was not part of the conversation.
I had the same problem last week. I would also notice that it would duplicate all my convos. The way I found to correct without the battery pull(because it will happen again) was just delete all your convos.