the door will not go dowwn with the remote control (but will go up) but will with the wall unit but you have to hold the button down while the door goes all the way down. When it is closed it will not stay close it opens. This door has a sensor that goes accross the door opening, does this have to be installed to for the unit to work properly? This is an opener that we took from another house and used as a replacement in this house (used the hardware from the old opener) Help if you can--Thank you