30 mile trip on last Thursday. Left home and got 2.5 miles, service shifter dinged on, trans tried to shift to P at highway speed. Shifted back to D, and continued. During the trip it started trying to shift to park more frequently, then 11 miles from dealership, it would not shift back to Drive, and had to coast into a parking lot to call a RollBack. Loaded it with difficulty an hour later, would not stay in Nuetral, Hauled 11 miles to dealer and I had to put it back into Reverse 7 times to get off the roll back. Was pulled into service on Friday, NO CODES. Test drove Saturday and service shifter message came up, but it did not shift gears! A Shifter Module has been ordered and a STAR Case has been opened with Technical. They say no cases like this on the New L is recorded? Grand Cherokee Summit Reserve L, 5978 miles when towed in, Has anyone seen anything like this? Shifter Module is over 5 days out on order? HELP?