DIAGNOSIS This is usually a moisture or grease issue. The capacitive touch panel can get confused if there's condensation or oily residue on or behind it.
FIX Unplug the unit. Use a slightly damp cloth (water only, no cleaner) to thoroughly wipe the entire glass control panel. Dry it completely with a microfiber cloth. Let it sit unplugged for at least 30 minutes to let any internal moisture evaporate. Plug it back in and try again.
IF THAT DIDN'T WORK There could be a loose ribbon cable connecting the touch panel to the main board. This requires opening the unit, which isn't recommended for most people. Time to contact support.
HEADS UP Never spray cleaner directly onto the screen. The liquid can seep into the edges and cause permanent short circuits. Always put cleaner on the cloth, not the appliance.