I have a Quadratic-Fire DV400S gas stove. Appx 14 Years old. When starting from cold it makes faint a high pitch noise similar to a dog whistle. It go’s away in a few minutes as the stove warms up. Is this something that can be fixed? I am not sure if it has always been this way or has just started. It is in a rental I own. New tenant is complaining. Any help is appreciated.