Visible sparks or arcing inside the microwave cavity during cooking.

Immediate action: Stop the microwave at once and unplug it.

User-level checks:

• Remove any metal objects, twist ties, or foil from the cavity.
• Clean the interior thoroughly, especially around the waveguide cover, using mild detergent and a soft cloth. Do not soak the cover.
• Inspect the waveguide cover for burn marks, holes, or cracks. If damaged, it must be replaced before further use.
• Check for chipped paint or rust spots; these can cause arcing and should be touched up with microwave-safe cavity paint by a technician.

Do not use the microwave again until any damaged parts are replaced.