To further explain what we think happened... We believe there was a bug such that when a user returned to PPQ after a previous session, it appeared to the user that they were logged in, but in actuality their login token expired. However, because we store user convos both client and server side, the user was still seeing the client side version of their chats as if nothing was wrong. Then, if that user deleted a particular chat, it successfully deleted it client side, but because they were not logged in anymore, the delete action never made it to the server side and thats why it persisted thereafter.
So why did your old chat just spray onto your screen again in duplicate? When you logged in again, it tried to retrieve any chats on the server (which were not deleted because of the aforementioned issue) and when it did, a react hook fired too many times causing the duplication (another bug we've now hopefully fixed).
Hope this helps you understand the situation a bit more.