After about six months of quiet operations, our new dishwasher has started making noises about 4 times times during the cleaning cycle. These noises, which last about 5-10 seconds, seem to happen when the dishwasher is draining. It is a sputtering, scraping, sound. It is not hooked up with the food disposer. I cleaned the cylinder filter and the fine filter. What can I do to clear this up?