21st Custom Coach Can't Join Dynasty

Once you have 20 users join it locks out the option for anyone to create a custom coach. It does not matter if the first 20 people all create a default, custom coaches or a mix. Regardless the last 12 users have to select a default user to join. Retiring a coach doesn't work around this solution either, you will just be forced to select a default coach as the coach doesn't retire. It just "retires" the user.