Ray posted a Dear Car Talk column today (8.8.2019) on the same vehicle, Jeep Cherokee, earlier vintage. That particular problem, the engine turns off for no apparent reason. Ray suggested, among other things, there may be a transmission component – said that particular 9 speed automatic has been problematic apparently – as well as a possible TIPM component. The dealership suggested it was an oil problem. In any event OP, good idea to read that column as it might provide some ideas about what’s going on here. Click “blogs” upper left, then “Dear Car Talk”.
The only other ideas I can think of:
Ask the dealership to keep the car and give you a loaner. One of their staff can drive your car as their daily driver for a week or two, however long it takes. This problem should happen to the staff member at some point, then the dealership won’t be able to deny it is happening, & will have to fix it under warranty.
Ask the dealership if they have a way to connect a device that will make a record of the engine rpm and vehicle speed as you drive your daily drives. If a patient thinks they have a heart problem that their doctor’s can’t verify it b/c it never happens at the office, the doctor will have the patient wear a portable device that records their ECG signal. When the patient feels the sensation they think is a heart problem, they are instructed to press a button, and the signal is stored in memory for later review. You need something like that for your Cherokee. Maybe some sort of test equipment like that actually exists. If it doesn’t, the would be a good product idea imo.