Go outside and make sure the slide is all the way in. It should be that when the outside flange seals against the gasket on the outer wall, thats what causes the slight "lift" on the inside. I believe it is actually a little "out of plumb" for that purpose. There should...if I remember correctly....be a gap between slides on the inside when both are full in. Your saying the carpet overlaps? I dont remember that.
P.S.
There are also some teflon "sliders" on the bottom of each slide out....make sure you havent lost one or more of those.
