Já bych flintu do žita neházel. U mýho mpx1 tohle tajný trojhmat vyřešil. (Total absolut brutal factory reset) :) With the unit powered down, hold the STORE button and power on the unit. Once you see a "d" in the display, let go and press the EDIT button once. Turn the data wheel until you see 2, then press STORE again.
The unit will reset and return to program mode.