Panasonic Model NN6381A
I can always enter the power and the time settings.
When I press Start, one of these three things happens:
1. The oven does not start and 88:88 appears in the dispplay
2. The oven runs for a few seconds, and then stops and 88:88 appears
in the display
3. The oven runs properly

What might cause this? Behavior #2 above makes me doubt that the
keypad is the problem.

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