This problem has nothing to do with RF or IR as far as I can tell. When a button is pressed and the remote registers that button press the LCD screen on LCD buttons will highlight the text next to that button indicating that it has registered the button press. When a button press fails the text on the LCD screen does NOT highlight indicating that the remote did not register the button press.

I haven't done extensive testing on other non LCD buttons but I would be willing to bet that when one of those buttons fail it doesn't register on the LCD screen either. For example, if you press the dedicated "FF" button on the remote it also displays "FF" at the bottom of the LCD screen. When the button press fails you would see no "FF" on the LCD screen.