A cooker can have more than one fan with different purposes. A sound associated with the grill may come from cooling rather than the main oven's cooking fan.
What the observation means
The source cannot be established safely by reaching through vents. Record the function running and whether the noise continues after it is switched off.
A useful next step
Leave the cooker unused if the sound is harsh, scraping or linked to overheating. Provide the timing and location for assessment. Do not block an outlet to see whether the sound changes or assume an unused oven means no fan should run.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.