A few in our alliance, myself included experience that our chats dissapear when we exit chat. For example if you exit chat, go to the map and return to alliance chat…the previous chats are gone. If you leave alliance chat and go to Peer support the same thing happens.
Had the same problem a couple of times, if I restart my phone the problem self-corrects. I think the amount of time we all stay logged in to the game caused occasional glitches.