Re-entering chat session

I have the following issue: we’ve published a chatbot with a certain amount of flows which can be closed by the user himself. The session will be solved from that point and the chatbot will be shown minimized (so the user can still have acces to it anytime).

However, when the user clicks on the minimized chatbot, no new session will start and the whole chatbot acts buggy (because we havent thought about ‘re-entering’ the session).
We want to show the user the first flow again, but we don’t have an idea how to fix this problem.
Does anyone know how to solve this?