mine has done the same on several occasions, and I've noticed that it can primarily be attributed to the angle of the coach, when parked during storage, and the slides are all in. Water finds easy ways to infiltrate anyway it can, even when you have slide topper awnings. If the coach is tilted/angled just right, the water can actually run 'around' the awning edge, into the covered area right above the slide seal, and thru any tiny gap in the seal, then into the coach, and either runs off somewhere from the top of the slide, or down the end edge.
Crazy, but true. I have mine in storage now, and added a rag at each end, right at the corner of the awning, so that any water would 'follow' the rag down the outside edge, and not back into and under the awning and top slide seal. Seems to be working.
'14 Palazzo 33.3 bunkhouse 34' diesel
KingTailgater2 Dish HD, 100w/5a SOLAR, BlueOx
100,000+mi since '14 - US, Alaska, Canada - Hiawassee, GA! (also, '14 Gulfstream Amerilite and '07 ForestRiver Rockwood) : )