Hi Mate, went through the same problem. Underneath all those shiny Switches its a tiny-little Tactile Push Button that actually does the job of connecting to the circuit. These switches are really fragile and sensitive. over time, they catch dusts from playing lib
Just like you I coudnt switch to HD Series and my warranty period was over as well. So i was brave and i opened the unit. not the easiest job in the world, but i did it. then with the help of my electrician friend, i took the actual push button out of the board. Needed a good soldiering iron for that. After that i ordered the same buttons (20 of them) from eBay. Then just replaced the ones that weren't working. I was desperate, so committed this suicidal mission. Worked out fine. But i am warning you, you need someone who is good at electrical or electronic repairs.
Hope it helps.
