Not famiiliar with your model, but if the slide has a four inch plastic pannel across it on the outside, look for breaks in the seal. If it has that type of construction, it's necessary to monitor it and pull out the old seal and replace with new sealant after 3 or 4 years.
Dick, Joyce, Diego, Picatso and Gustav
2017 3720 RL, and 2013 HC 343RL
Pullrite Hitch, IS, Disk Brakes, 3rd AC, Winegard Traveler, Bathroom door mod, Dometic 320, couch for desk swap, replaced chairs, sun screens, added awnings, etc.