Make sure the RV is level.
Also they make these little 4-6" wide by 4' long plastic things that the slideout glides on as it comes back inside the RV. I have them with my fifth wheel because the dealer that sold it to me used apparently had some issues with the biggest slide digging into the kitchen floor as it retracted.
Making sure the RV is level should solve the problem. If you have the six point auto level system like I do it's really easy to go outside just before you bring the slides in and hit the Auto Level button one more time. It's become a part of my routine.
