Yesterday I was strolling through our local Toyota dealers used car section when I noticed various models parked together with a notice in the windscreen saying "catalytic converter already stolen, awaiting parts"
I believe they are related and check VSC (vehicle stability control) can come on for various reasons. Probably the most common is an O2 sensor. Best to get it scanned for a code otherwise you're be just guessing.
I would doubt the clock spring is the culprit. What you describe is identical to the horn problem I had with a previous LS. It would only work with the steering turned left or right with the engine off so the steering was tight. I even replaced the clock spring! It turned out to be an earth problem. I took the plastic covers off the steering column and added a wire from one side to the other and it worked. Hard to explain like this, and somewhere in the bowels there's a post I made years ago. Just play around holding a wire to a column bracket and grounding to the body/bolt head where there's no paint.
The RX450h is still a car that gets my attention, but I'm not sure the rear space (for a large dog) would be any better than my estate. Maybe if you get a chance you could measure the height of the boot floor to the headlining? It's also hybrid failure that concerns me, although I guess Lexus are maybe better than most.
Looks very nice, and for a car of that age the MOT history isn't at all bad, although I would want to know how well the corrosion work was done that caused an MOT failure.
He's a lovely boy, only had him for 8 weeks and he discovered the sofa in a matter of days. A perfect house dog, he absolutely loves people, squirrels are another issue! He retired last December and won his last race!