I'm guessing when your player stops, sometimes it's not on the floor. That's why your 4th event is not working. Try changing it to "Platform NOT moving and Platform on the floor". Check that your walking and idle animations are looped.
Also, this can happen when different frames in your character have different origin image point coordinates or different collision polygon shape. A common practice if to use an invisible box sprite with platform behavior, and pin your character sprite to it. Then you will not have such issues.