I had the same thing happen two weeks ago. I went to Sam's Club to get a gallon of gas for my lawn mower. I walked around to open the lift gate. It only went up a few inches. "Weird, I thought." I parked in the parking lot and went into Sam's. When I came out, I tried every way of opening the lift gate. All resulted in it opening only a few inches. On the way home I was thinking that I should drive right to the dealership, but I had ice cream. I stopped and dropped off the ice cream. I went back out to the driveway and once again I tried every way to open the lift gate AND THEY ALL WORKED with no problem. I decided not to take it in and it has never done that since.
The button to set the height was not set, nor even touched between the two incidents. It was just a strange occurrence that just happened with no explanation. I didn't break it, I didn't fix something, it just was what it was. Quite unexplained.