Answer to "mute button does not work"My logitech harmony 700 had the same problem for more and more buttons. After opening it, I discovered house mite on the print under the metal discs. They prevented the electrical contact between the disc under the button and the copper of the print. All mite were already dead and pressed flat. I cleaned everything and closed the hole in the print for every button with some epoxy to prevent mite to creep in again. Everything works fine now.