I have a thermador prg364gd. The oven will not heat past 200 and there is a little gas smell. Sometimes the oven will heat upto 350 or whatever I put the temperature too but this happens only sometimes. All four burners work just fine.
Searching another website I foud someone had a problem with their RGB745 -they stated the problem was, "The oven only heats to about 200 degrees, on rare occasions it might work fine for a week then won' heat over 200 again."
The answer posted (this is a direct quote) - "Open back cover fix the nozzle by push neddle to smal hole where gas passes/clean clean also burner holes/ check the gap between nozzle and burner, does incline with the guide.cover it and test oven."
This sounds exactly like the problem I have only a different model, however I really don't understand the answer that is posted. If this is the possible problem I would like to try this because I think you might come back with it's the thermostat sensor. Please let me know what you think.