When reassembling the unit, take special care to reseat the control knobs back onto their controls on the circuit board.

First, remove the small plastic cover holding the control knobs captive. From the bottom, release three plastic tabs indicated in red. Then slide the small plastic cover forward, to release the two plastic tabs indicated in yellow.

Reseat the control knobs back onto their metal posts.

Replace the small plastic cover by inserting the two tabs (yellow) and pushing down to reseat the three tabs (red).