Solved! According to Logitech, it's not possible to issue continuous commands by pressing and holding the button, when you have assigned different functions for this button depending on whether you short or long press the button: http://forums.logitech.com/t5/Harmony-Hub-Based-Remotes/X1-box-holding-down-page-up-down-button-doesn-t-scroll-through/m-p/1352505#M17478 Based on the above I assigned the Page Up command for both the short and long presses of the ChannelUp/PageUp remote button on MyHarmony and this fixed it.