I have a 2018 GMC Yukon SLT. The smaller(40) seat backrest is locked in the folded down position and I cannot get it to release. Also, the seat will not release from the floor to the tumble position. The power release button goes thru the steps but nothing happens. It sounds like the seat is stuck and in a bind. I've tried everything to get it to release including my entire body weight and trying to rock, push and pull. Driving me nuts and trying to prevent taking it to the Dealer. Any ideas would be greatly be appreciated.