The woman pauses to allow the man to exit first, the man pauses to allow the woman to enter the elevator first. After a couple of seconds of just standing there, they both make a move for the door - but as each sees the other moving, they pause again to allow the other to go first.
More standing still occurs until finally the door starts to close.
The man in the elevator jabs his arm out at the last instant to prevent the doors from closing, and the two stumble past each other as they simultaneous switch places.