My 2018 Cyclone 4200 also had a rotting slide along with poor slide roller placement. My rotting slide was the bedroom slide, the reason for the rotting was due to the slide placement to close to the roof line. You are not able to install a slide cover. When it rains the water just rolls down the sides and water moves under the slide. putting the slide in lets the water just soak into the wood at the joints. Yes the bottom was/is coated with a black sealant but wont totally seal the joints.
My repair was minor compared to some I have seen. With my rollers out to the edge along with dampness caused the wood to start breaking down. The shop I took it to in Clearwater Florida installed 3 stainless steel plates (the whole length of the slide) on the outside floor along with large amount of Silicone sealant has saved the floor and made the slide roll in and out so much easier.
Now the living room slide was a different story there was no rotting wood (because of slide awning) but the slide was always shifting side to side when going out or in. The same mechanic told me it was from the main beam that ties the slide to the slide arms. The factory (Lippert) uses a 3/4 channel steel beam welded to the actuator frame, so with the weight of the residential fridge, dining table and chairs and the recliner sofa on that slide. When the slide starts to move one actuator can move a little before the other causing the beam to bend. Mechanic stated Lippert change from 3/4 channel to full square beam years ago because of that problem, he also stated he did not know why or when they went back to the 3/4 channel. He removed the bent 3/4 beam and welded on a full square beam and that cured my problem.
Extended warranty would not cover the charges because it was not repaired like the factory manufactured. It was repaired to be better, those 2 repairs were done to the tune of $2000.00.