I've got a similar problem. Did you ever find a solution?

-- Dan

Dan,
First remember to mark all terminals and don't rush - ALWAYS UNPLUG THE UNIT FIRST. At one point I had been switching around the igniters to see if I could isolate the problem. I had been swapping around the igniters/wires back and forth and one time forgot to unplug the unit. When I removed a wire and fryed a terminal. It did not hurt the control module, but if the arc was to the copper gas line there would have been a BOOM and I could just hear people saying "that's why you shouldn't do that kind of stuff yourself - dummy".

The problem was the igniter itself. This was actually my sisters problem over the years that she would tell me about when I would visite every couple of years and this year while visiting and on a free day I took it apart. She actually had several thermador certified appliance guys come out over the years. One guy told her it would be cheaper to replace with a new unit and another told her parts for that unit were not available any more. Anyway I took the igniters, high temp wires and the switches under the knobs to this very helpful appliance parts store and the owner tested them (only with an ohm meter) and said they were good so it must be the controller. Prior to this I took everything apart and sanded/cleaned all terminal connections and grounds but the problem was still there. FYI my sisters stove is pretty much spotless unlike mine. Anyway the parts guy crossed reference the controller module made by the same company (module company, not thermador) and told us to give it a try. My brother in law said it had been driving them nuts for many years so he was happy to spend the $100+ bucks on it. Well after connecting the controller module and puting everything back we fired it up, only to have the problem to continue as before. Since there is basically only the module and igniters I figured it must be the igniters even if the parts guy said it was ok. We returned the controller (the guy was nice enough to do so, most places won't on electronic parts) and the parts guy found a set of thermador igniters for us. They were not the exact same one's, but the height was similar and we had to modify the retaining clip a little. This finally solved the problem, but my sister was very happy because although the sparking did no harm it was irritating. Maybe the repair guys are not willing to spend the time to cross reference stuff or don't know how or maybe it is just not cost effective for the customer if they do this (spent a whole day going back and forth to the parts place).