If it is like mine. the outside screws at the lower bottom that holds the frame in have worked out a little and allowing the that edge to kick out to the outside and the slide is bottoming out on the inside and causing drag as it is coming in The gears is grinding because of the out of alignment stress being put on it. When taking the slide out, there is not the same type of stress being put on the wall assembly. To help get the slide in more easily and to have a better alignment, have someone on the outside gently push the slide in at that area and the all side/corners should be snug to the seals. Look at the screws on the outside beside the slide where the framing is. do any of them look 'backed out'? The weight of the slide is 'stripping' the screws through the metal. More and larger screws will need to be installed. Have your dealer or an RV shop look it over and give advice on repair.
2013 Forest River Salem Hemisphere SBT312QBUD
2001 CrewCab F-250 7.3 PowerStroke Diesel
SuperChip, BTS transmission, 6.0 Trans Cooler