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F12 means that the logic in your display board is corrupted. If you turned the power off for 5 minutes and that didn't reset the issue, there is nothing you can do but replace the display board to resolve this issue. Now depending on the exact age of the oven, if it's less than 1 year old warranty will come out and replace the part at no charge. If it's over 1 year old, you'll need to order and replace the display board because it has failed I'm sorry to say.
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