This is usually a bad touchpad. The way to tell for sure is to kill power to the unit, take the control panel down and unplug the ribbon connector that connects touchpanel to the clock. Put it back together and reapply power. The clock will just sit there blinking and, obviously, the buttons won’t work, either. Wait the length of time it takes to leisurely swill a decent beer, such as Tuckerman’s Pale Ale. If your beer drinking reverie is uninterrupted by beeping, then the touchpanel is bad; come git you one.

If it still beeps, then you have a bad clock.