I've had the same issue, and am trying to identify 'exactly' where the outside leak is coming in, which for my coach seems to be at the ends of the main full wall slide. I've noticed it before, but it seems to be really increasing in the amount, even though the slides are 'in', and should be well sealed. We've had a lot of rain over the last week, and it's given me the ability to check it every several days and try to 'see' where it's coming from, as I have a puddle under the end of both ends on the floor.
I've noticed that the ends of the slide's awning reaches well past the ends of the slide room, but I can only imagine that water, and it's adhesion properties, can still cling to the edge and underside, before dropping onto the edge of the slide, and the top of the seal. I can also imagine that, while it seems to be sealed, water can find ANY where to intrude when it can - a simple pinhole will allow a lot of water and drips over a long period.
I also imagine that since my coach may 'lean' toward the left, while it's in storage on gravel and not necessarily totally 'level', which makes the main slide side lower, that water from the roof, and the slide awning, now has more of a 'slope' to ride along. If I was more 'level', I imagine this would not necessarily be the situation, or might not result in as much water coming in.
While we've not experienced this same issue when traveling or using the coach, I imagine that it's a combination of the fact that while moving, the rain is not reacting the same as water sitting on the roof while it's parked/stored, and when we have the slides out, the same problem is not evident.
I've seen water behind the driver seat on a few occasions, usually after bringing in the slide after a rain, when water on the outside of the slide walls is then brought 'into' the coach, and then drips down onto the floor... that makes sense, though it's usually not that much.
My situation make require me to stuff some rags or towels at the top corner of each end of the slide, to keep the dripping water from the roof/awning from working it's way back into the top of the slide, and into the coach... maybe : /
'14 Palazzo 33.3 bunkhouse 34' diesel
KingTailgater2 Dish HD, 100w/5a SOLAR, BlueOx
100,000+mi since '14 - US, Alaska, Canada.... formerly Georgia, then NorthCarolina, now Alabama : )