Leaking through bottom of slide

So, I purchased a used Class C Coachmen a couple of weeks back and today was our first heavy rain. I guess you know what's coming next. No leaks in the roof or windows, however there is water coming out and across my kitchen floor, which thankfully is linoleum.

I can see exactly what's happening, which is that rain is falling onto the roof of the slide, coming down the side of the slide and then pooling at the bottom corner where the big gasket is. A lot of the water is falling away as it should, but a solid stream is also running the other way, directly into my coach under the stove. I am completely level, by the way.

I have fixed the problem temporarily by putting a tarp over the entire slide, and I guess I could have unleveled the RV to make all the water pour the right direction, but neither of these is a solution.

I've heard some talk of slide awnings, but am not sure if this would solve this particular problem, so I wanted to post here and see if you have any ideas since you always come through :)

Thanks in advance for any advice