Thermador gas range was built around 2001, I purchased it back in 2009, worked pretty well all these years.
About a year ago it developed the issue that it started to randomly spark even with all four burners off. I replaced both Ignition Switches on the XLO burners, which solved the problem, everything was back to normal.

Now it developed another spark related problem:
- no spark at both XLO (left) burners, no gas flow
- continuous spark at both regular burners while lit
- no issue while off (so different problem from the one a year ago)

Step one: I replaced the 4 point RI 324 spark igniter module with the 6 point RI 306. Now I have a solid spark at all four burners while trying to light the flame, normal gas flow, but it keeps sparking all four igniters if any one burner is lit, regardless if XLO or normal burner.
If I turn one of XLO burners to low, it sparks while the flame is on, stops when the flame is off, and sparks continuously again when it re-lights the flame.

Considering that the Spark Ignition switches on both XLO burners are less than a year old, and the spark igniter module is brand new (albeit a different model number as the original RI 324 is no longer available), what would be a sensible next step to check?

Thanks a lot