We've been satisfied with a Sanyo convection oven for four
months. Now I have to turn the temperature setting to maximum to
roast chickens and fishes. The filaments tend to glow dimmer than
usual. Usually it's bright orange, now it's dull orange. I notice the
decline in performance when a chunk of melted butter soaked the
lower filament. What can I do to increase the filament glow?

Thanks