imessage randomly removes messages from conversation without prompting

My imessage is deleting entire conversations at times once I receive a new message.

I can have a conversation and suddenly the person will send a message and all the old messages go away. This happens randomly, sometimes with conversations that are short and sometimes for longer ones. I normally chat with people who are on their iphones, but they haven't had this problem with other people that they text via imessage.

It's very annoying because someone can send me 4 or 5 messages in a row and by the time I click over to imessage only 1 message is there and all previous messages from both of us are gone. This can also happen if someone sends one message- all previous conversation deletes and the one message they sent becomes the only one in the conversation.

Many times these are messages that I haven't read, and some are messages that I wanted to save (phone numbers, addresses, etc that were messaged and I hadn't had time to copy and paste elsewhere)...I don't know if they exist somewhere, but I haven't been able to find them and just need to know if there is a fix for this at this point because it's very annoying because this was a very convenient messaging service until this issue arose.

I mainly use imessage through my macbook and am not having problems with this on my iphone. I also checked to save history when conversations are closed in preferences but it doesn't seem to make a difference.

Also, the messages used to go to both my phone and computer, but now only go to one or the other (the settings on my phone have send and receive to 2 addresses- the phone and my apple ID). I don't know if that's related.

I noticed there are a few questions about this online so people are having an issue but have yet to run into a fix for it.