We had a similar issue with the bedroom slide on our 2003 Marquis.
The slide frame was the issue here, and remains an issue until I can get it realigned in Bend. The bolts that attach the frame to the floor via four upright posts and hold it into position have loosened allowing the frame to have an uneven alignment. This is literally where the slide attaches to the coach, so if there is any wobble or sideplay the slide with work against this as it extends and retracts.
The upshot was that the slide remains flush with the coach body when retracted, but it works hard coming in or out, think of pushing on one corner instead of in the middle of the slide. So all the slow groaning and creaking was lessened with tightening the bolts. Beaver also did a halfazzed job of attaching the four uprights to the floor, with different hex screw diameters used to tie everything down.
To be fair, I am the 4 owner of this coach and have no idea if I'm looking a previous repair, although it looked untampered with since the carpet on top of the trap door allowing access to the aft end of the slide frame was uncut, meaning you couldn't open the access door if you wanted to.
So evidence is that one hole on the side with the most force on it is oblong from being worked by the loose frame/slide until it worked itself a half inch from where it ought to be. So, bottom line, look at any bolts in the slide mech for slop and tighten them up, check the motor mount bolts too, they worked loose. It appears the only way to square the slide is to loosen all bolts, support it on the outside and square it up, then tighten up the fasteners. There should by all rights the a pair of adustment screws on each leg of the frame to allow this to be done on the inside; a useful modification. As it is, it will have to wait for a shop to fix it better.