Bedroom Slide Loose?

[Tank]

Hi, Folks!

When my BR slide is in it seals well around the entire perimeter. But, when I start to extend it the top tilts in noticeably and doesn't seal against the interior frame. I can reach over the top of the flange and put my fingers between the flange seal and the inner surface of the frame.

I'm thinking I need to remove the bed and the bed support and investigate. I've looked at the parts book, but it really doesn't show how the slide "box" is mounted to the "sled." So, am I on the right track? What should I look for?

Thanks!