I can confirm on my Dec 2016 Model S passenger seat being stuck, was taken to a car wash and seat was moved all the way to the front, then it got stuck , barely moved back on the right side but the left side didn't so afraid it break if forced, I read curtvb and beatle up above with picture, i raised seat and i tried to align seat then went below seat I removed the shaft from both sides it's flexible , tried to put back in the left side which wasn't moving n wouldn't go back all the way in, I barely touch the motor to move seat and then tried again and shaft went all the way in and then I put the motor side in , it's a flexible shaft , now seat is working moving back and forth
Thank you @curtvb and @beatle
Thank you @curtvb and @beatle