Welcome.
That's one hell of a first post....
You sound like you have above average DIY skills and I'm sure you'll nail this issue too, just in time for the next one to pop up.
Is it possible the steering angle sensor has a dead spot? Perhaps get the front wheels of the ground and turn the wheels lock-to-lock while looking at the values in INPA - these SAS units are known to wear out. There's a repair kit on eBay.
Although not normally at such a low mileage - but you've had a number of other failures on that car that are also odd for such a low mileage.