Have you tried asking Thermador if a service manual is available? Or ask for the manual's part number so you can search for it.
I have called them several times. Once, I was accidentally connected to a tech support guy, but that is for commercial use only. He said he wasn’t supposed to speak with me, wouldn’t give me advice, but did answer some questions. That’s when I learned the big dial on the front doesn’t do anything useful.
I now keep a thermometer in my oven, crank the dial to 500 and monitor the temp every 15 minutes and adjust accordingly. Kinda sucks because the oven wasn’t cheap.