Passenger side, stair slide

1999 holiday rambler 40' class A. At the top of my steps to get into the motorhome there is a slide out that seals the top of steps so the passenger has a place to put there feet while driving. It slides out just fine, but when pushing the button to retract it it doesn't move. Also at that time there is an air leak coming from the front end. I pulled out the generator slide and found the source of the air leak. I was thinking it was a broken air line or something. Off to the side in the front by the generator there is a small little junction box that has 3 ports with 3 air lines going to it, and one open port with nothing. When you go to retract the step slide there is a lot of air coming out of the open port. The air leaking last for about 30 mins or so ... then you can push the slide in and it will stay open.