I am having this same type of issue. I went through several support messages and they determined there is not a bug in their system. The person I am trying to add is a cleaner and helps people manage their listings, they have no idea what a hosting team member is. We tried to use another email for the person, but then it asks them to use the email that gets the error message. Airbnb needs to add levels of access to their calender, for example, perhaps the term "co host" is to broad, because cleaners need access to the calander as well and in many cases the cleaners work with several airbnb listings. This is something that could be fixed at a programming level, perhaps just adding in a level for "cleaner" or a person to have access to the calender without falling under co-host or hosting team member.
There are dozens of messages on this so somehow the programming is causing access errors. Our next step is going to be to approach airbnb tech support from the persons account that needs access to see if it is labeled incorrectly... not sure why this particular account is popping up as a "hosting team member" account but obviously that is creating a massive amount of problems within the system.