Diagnosis
The clock/memory circuit is losing power. This points to a faulty or weak capacitor on the main control board that's supposed to provide temporary backup power.
How to Fix It
There's no user fix for this. The component responsible is a small electrolytic capacitor on the control board that acts as a mini-backup battery. Over time, these capacitors can dry out and lose their ability to hold a charge, even for the few seconds it takes during a door operation or minor power dip.
If That Didn't Work
The entire control board may need replacement if the capacitor failure has caused other issues, or if tracing and replacing the single capacitor isn't feasible. The clock resetting is annoying but doesn't usually affect the cooking functions.
Heads Up
This is a common age-related issue in many electronics. It's a sign of general board aging. If other buttons start becoming unresponsive or the unit behaves erratically, the control board is the likely culprit.