I am having the same issue. 2020 AT4 since Feb of 2022 28000 miles my truck has been in the shop for 97 day's. They have replaced my entire DEF system, transmission after replacing multiple modules. Crankshaft sensor. Still not fixing the shuttering problem. Now they've had it for another month...
I have a 2020 AT4 and absolutely loved it up until March. Now I'm having constant transmission issues. Started out. I'd be running down the highway at 80 and it felt like you ran over a speed bump. Come to find out. For some reason the transmission is downshifting but immediately shifts back up...