Microwave interior sparks or arcs during cooking, especially near the walls or around the waveguide cover.

Safety first: Stop the microwave immediately and unplug it if you see sparks.

• Remove metal objects: Ensure no metal utensils, foil, or twist ties are inside.
• Clean the cavity: Once cool, clean the interior with mild detergent and water. Pay special attention to the area around the waveguide cover.
• Inspect waveguide cover: The small rectangular mica cover on the side wall should be intact and not burned or cracked. Replace it if damaged with an Oster-compatible waveguide cover.
• Touch-up paint: If cavity paint is chipped down to bare metal, use microwave-safe cavity touch-up paint to cover exposed metal after cleaning and drying.