Our 2011 350 main slide was leaking, tech said there was a void in caulk in the center of the slide. One bolt was missing in bracket holding slide topper. They caulked around the topper brackets and removed screws, caulked in screw holes, replaced missing screw and caulked void. Ours would only leak in some situations not all the time and not with slide in. Hasn't leaked since but just had repairs done. Hope this helps.
Rudy - 10 year old long haired dachshund
2011 Georgetown 350TS
2013 Chevrolet Equinox toad