Unexpected gear downshift accompanied by a temporary rear wheel lock-up. This occurs at highway speeds and has shifted from 6th gear to 2nd gear multiple times at 50+ mph. This causes substantial safety concerns to both those in the vehicle as well as other vehicles on the road in the immediate proximity. When this occurs speed is restricted suddenly/immediately by a reduction of 5-12 mph. This causes severe impact to passengers. At low speed the gears shift sporadically between all 6 gear ranges impacting drivability. The vehicle has been inspected several times by Corwin Ford however they clear the codes and ‘can not replicate’ which correlates to the dealership deeming it safe to operate. There were multiple warning lights/lamps, messages when delivered to the dealership. Those were then cleared prior to ‘diagnostics’ as that was ‘their process’.