[Motor31]

It sounds like the roller on the front has either dropped or was never placed properly. You can go outside and peel the wiper seal away from the bottom of the slide at the notch and look at it. If there is a problem there the slide will have to be jacked up off of the roller to fix it.

Is there an obvious tilt to the bottom of the slide in relation to the rest of the opening?

Another place to look for a problem is inside the pocket door between the kitchen and living room. There is an aluminum angle piece that the weight bearing portion of the wall rides on. There is a tendency for the angle aluminum to back away from the wall and allow the plywood to rest on the roller there, crushing the wall a bit. Shine a flashlight in the gap on the kitchen side of the opening and look at the bottom to see the aluminum angle piece.