I have downloaded the AVR-S570BT code base and the volume when pressed and held goes down continually till released on my Denon. From your first post you appear to be programming it correctly “Currently the button mapping has no "long press" action selected”. Also the fact that your issue happens in Devises Mode indicates something else is wrong. Have you tried moving the Hub/Blasters around the room? It could be a line of sight or interference problem.