Hola Laura and Ken.
I have got the same problem since November 2019. I removed my host from the list, but she still receives the messages. And the name of my ex cohost appears in all the Airbnb massages guests.
I am calling and sending messages to Airbnb customer care almost every day and they say that is a technical problem that they are trying to fixe. Almost 4 months and no solution.
It is a little bit crazy for me and my ex cohost.
I have read in other guests with trouble with the cohost system, but are different to our problem.
Saludos desde Málaga. Ángel.