My 2008 MKX appears to have intermittent Transmission problems on long trips

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After driving almost a 1000 miles my MKX does a hard shift to a lower gear. This jump shakes the whole car and feels like the transmission has broken. From here on in every time I go up a hill or accelerate the same thing happens. Revs go from 2k to 4k and remain there until I get to a constant speed. If I pull the car over and turn it off the problem corrects itself for the few hundred miles. Wrench led comes on but no code is detected at the Lincoln dealer. Had them update the software and do a trans fluid change but the problem re-occurs. Lincoln dealer could not find any problem with the vehicle.