I had the same thing! At the PDI I saw daylight at the bottom of the slide when it was closed. The issue, fixed by the dealer, was an outside body molding that should have stopped just before the slide but wasn't. When the slide was in it overlapped the molding instead of sealing against the side. The fix was to remove the molding cap, cut back the molding with a dremel tool and reset the cap with caulking.
Now that you've had the ongoing leak, water damage to the subfloor seems certain. Check for swelling. This has to be repaired soon.
I'm wearing trifocals now but my hindsight is 20/20.
Bilsteins and Sumos front and rear...HUGE! FatMat and Hoodliner...HUGE!
Hellwig sway bars F&R, 235/85 Hankook ATM, alignment...HUGE!!!
Battery watering, 260watts Solar and BigFeets to make life easier.