So, Im not sure how this works but I just bought this unit. The adjustable wattage and voltage is nice, but Id like to lock it and it doesnt seem to work. The manual states that I need to hold the up and down buttons simultaniously for 2 seconds to lock it and then it will show on the screen it is locked. But when I try to press both buttons at the same time (obviously difficult to do on its own), it start moving the wattage up or down quickly until it tops or bottoms out its value. Anyone know anything about this ?