In desktop messenger, messages now only goes back a couple of weeks and not the few months it used to.  One of the many things that has been quirky different about messenger.  Very frustrating.  But really cool feature and tool.  i called customer service and a very nice lady helped me and she couldn't understand why it was doing what it was doing either and turned in a ticket to your technicians.  Well, after several text updates that they are working on it, a final text that it was closed.  Not resolved but closed.