I just bought a used 2017 Yukon XL Denali. Great car, I love the ride. Earlier tonight I lowered the third row passenger side seat down by pushing the button. It went most of the way down... and stopped. Now it won't budge up or down. It responds to the button by shuddering a little when the raise/lower button is pressed, but that's it. I can't move it at all by hand. Any ideas????