DIAGNOSIS The internal backup capacitor on the main PCB is dead. This capacitor holds a small charge to keep the clock memory alive for a few minutes when unplugged.
FIX There is no user fix. The appliance must remain plugged into power to maintain clock settings. The cooking functions are not affected. You can simply ignore the clock and set the timer manually each use.
IF THAT DIDN'T WORK If the unit also loses other settings (like preset favorites) while still plugged in, the main PCB itself is failing and may need replacement soon.
HEADS UP Do not use a mechanical outlet timer to turn the appliance on/off. The power surge when the timer clicks on can damage the sensitive electronics. Always use the unit's own power button.