I have a different problem my MCU Pro and Xtenders: For a couple of years, when I powered up, the faders went through their usual calibrations, pull down to the bottom, and are ready to go. Recently, for no reason I know, the main unit and one of the Xtenders go through calibration, but then one fader on each unit moves up to the highest point and buzzes as if straining to go higher still. So I have to power them off and on again, and sometimes twice before they are ready. What's up with that?