Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Burner & fan assembly removed from appliance

Observation:

Check burner is clear and unrestricted
and in good overall condition.
Check the insulation panel is fitted
securely and in good condition.
Check for any perceptible movement of the burner within the front plate. If required dismantle burner plate and replace the burner mounting gasket and burner plate seal if necessary.