Hi Tom, did your steering wheel button act up again any time later?
This happened to me 6 times since I bought my Model S last year. Every time they just replace the steering wheel buttons, airbag assembly and they get fried after a couple of months again.
It happens mostly in the winter.
The symptom I see before the buttons will get fried is that the right side display of the driver's dash screen will randomly switch to a different app without me touching anything. When this happens a few times, I know the buttons will get fried soon.
I am frustrated with this issue now and trying to negotiate with Tesla to replace my vehicle as they clearly do not have a solution to the problem.