I have had this reverse problem several times since purchase. Mine happens when both on an incline and on level ground, always after letting the car sit for some time. I have taken to the dealer twice, latest on Feb 4 and am now waiting for Ford to tell them a fix. I called Ford customer service today 800-392-3673 and informed them as well and am now waiting for a reply from them as well. I recommend that everyone that has had this problem take their car to the dealer to investigate as that will spur Ford on to find and fix the problem.