A loose, damaged or incorrectly fitted knob can make the indicated selection uncertain. Do not assume that its printed pointer still represents the control position accurately.
What the observation means
This is particularly relevant after cleaning or a previous repair. The visible knob and the mechanism behind it are different parts, and turning harder can worsen damage. An uncertain Off position is a reason to stop using the appliance, not to mark a guessed replacement position.
A useful next step
Leave the control undisturbed and report what changed. Use a safely accessible isolation control if needed. Do not remove parts, grip a spindle with tools or try to identify live settings by whether the cavity begins heating.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.