Note the two modes, settings and timing. A symptom associated with simultaneous use provides different evidence from a fault in either cavity used alone.
What the observation means
Do not deliberately repeat an electrical trip or overheating event to prove the relationship. Shared supply, controls and cooling arrangements require competent assessment. A larger cooking load also creates more heat around the appliance.
A useful next step
Leave the cooker unused for hazardous symptoms and explain the existing sequence clearly. Include whether the hob or grill was operating too. Do not change protective-device ratings or limit use to a guessed combination as an unassessed workaround.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.