My 2015 Yukon SLT is having this same issue. The driver seat has a slight shifting feeling on turns. Haven't taken it to the dealer yet because I know its going to be hard for them to feel what I am feeling driving it everyday.
On another issue, both my break lights are getting condensation in them on cold days and after a wash. Spoke to the dealer about this and they said they need to see it but the condensation dries quickly when you drive it. Just another frustrating problem with this vehicle. I will be starting a separate thread on this to see who else is having this issue.