The container, depth and heating method can expose the edges more strongly than the centre. That pattern does not identify a specific failed oven component.
What the observation means
A shallow portion and a deep covered dish need different handling. Some ovens offer a dedicated reheating or steam-assisted mode, but its instructions must match the food and container. Reusing a grilling setting because it seems fast can brown the surface without thoroughly reheating the contents.
A useful next step
Follow suitable reheating instructions for the food, including any stirring or standing guidance, and do not repeatedly reheat unsafe leftovers to investigate the appliance. Record the selected function and whether the same problem affects fresh cooking too. A wider failure across familiar, correctly loaded programmes is stronger evidence for repair assessment than one difficult reheating arrangement.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.