Our 2015 XT (140,000 km) has recently begun to "stutter" (I can't think of a better word) when climbing mountains. We'll be driving along the highway at 100 km/h and then begin an ascent, and there will be 3-4 seconds where you can feel the vehicle "stutter" (or convulse) significantly before it figures things out and then accelerates. Someone who knows cars better than I do was with us once and said he believed it was a transmission problem, almost as though the vehicle was having trouble deciding which gear it should be in. Has anyone else had this issue? Thanks.