Both the microwave and convection aspects appear to work, but the convection alone doesn't get as hot as expected. Examples: cornbread at 400-425 deg not nearly cooked (1/3 cooked?) after 20 minutes, preheating at 400 deg said to be complete in less than 5 min, but red-hot bar at back of oven only noted in last few seconds and inside of oven merely warm to the hand (not touching edges).

Is there a test that can be performed to check that the convection operation is performing properly or not? Another approach? Thanks!