I have a Gaffers and Sattler gas two door wall oven in my mobile home circa 1978 or 1979. I noticed another post with a similar problem, but didn't know how to access the response--if there was any. If I set the temp for 350 it will jump to 400 or more (I use an oven themometer), then I turn it down and it will go down to 300 or less. After a while it will sometimes stabilize and maintain the desired temperature. Are parts available for this oven or will I have to replace it. Thanks for any help you can provide.