I've always wondered if the steering system was changed with the refresh.
There's so many of us experiencing this problem I was hoping Tesla would issue a TSB on the problem.
Have you had your SC look at the problem?
I took my 2017 refreshed-fascia S 60 to the SC yesterday to have some issues looked at, one of which was a misaligned steering wheel, with a mushy feel somewhere between the 10 and 2 o'clock positions. When you're driving straight at 30 to 70 mph, I get a mushy feel to the wheel if I perform a steering adjustment between about the 10 and 2 o'clock positions. If I perform a full 90 degree turn, like at an intersection, I don't feel the mushier feel. I always have it set to Sport mode and expected the steering wheel to have a firm feel all the way through a turning maneuver. I asked them to check the car's alignment, toe in, camber, etc.
The car came back from the SC with a straightened up steering wheel (no longer tilted to the left even though the car is being driven straight). The steering wheel's feel seems to be better, but still not as firm as I would expect.
As a point of reference, the older P85 loaner that I was provided had a firmer feeling steering wheel than my car, also set at Sport. I relayed this to the mechanic, and he told me that the older Ss have a different steering rack altogether. Thus, the steering of the two car's would likely feel different. Has any one else noticed that the Sport mode steering for circa 2017 refreshed cars is mushier, or less firm feeling, than for the older nose cone Ss?
I will continue to monitor the issue. Just sharing for your info.