I’ve been struggling with this as well. I did work for me with the script you mentioned in your first post. Suddenly not anymore.
Today I saw a post in the Mini Media Player section on the forum. There was mentioned that the selection of a station in your favorites will not work when your receiver is added under the Yamaha Musiccast integration. So I tried to add my receiver as under the Yamaha integration. I tried the script and it does work now!