I just replaced 3 patio doors (19 year old Marvin's) last week with Andersen Frenchwood gliders (these are the 400s). They were installed by a licensed contractor. I think they are garbage. They look good but mine are performing poorly. Major cold air infiltration at the top and bottom of the interlocking weatherstrip between the panels. In fact, I have an adjacent 1 inch strip of frost the entire length of the interlocking strip. I have resorted to stuffing t-shirts in where the panels meet to help stop the cold air. I feel air getting in along the bottom of the moving panel and have thick frost on the sill. Also have frost in the sill channel. The sill is just shaped metal with no insulation. I have the auxiliary foot locks and cold air just streams out of the lock holes in the sill. I have had to plug them with a paper towel to stop the air.

My old Marvin's were much better. I don't know about Eagle but if I knew what I know now I would have stayed far, far away from the Andersen's.

Jeff-
I suspect your jambs are bowed not allowing the interlock between the panels to do it's job. First check the stationary panel is even with the base it sits on, then take a piece of string and stretch it tight on the lock jamb.

If both are ok then check for the rubber pads both top and bottom on the stationary panel interlock. Last close the door and lock and see if any light is visable thu the interlock, if so the stat panel needs to be pushed in tighter to the operating panel..
Just because someone is licensed doesn't mean they did it right.

I prefer the Pella sliders with the sliding panel on the outside. It does give a tighter seal when the wind blows. The drawback is that the screen is on the inside, however this does allow for a longer screen life as the screen is protected from the weather