I have the same problem.
I think the rain comes in on the ends when it rains.
It doesn't seem to roll up as tight as out manual awning did.
Lots of wrinkles.
I cleaned mine real good last year and when we went out a few weeks ago I was shocked when I unrolled it.
Mildew all over the place.
The best idea so far is maybe using a large plastic soda bottle.
Cut the bottom out of it and slit the side so that you can slide it over the ends of the awning. (slit facing down)
I haven't tried this yet but after I clean up this mess I have got to do something.
We can't roll it out without moving the trailer out of it's storage spot on the side of the house.
It's a real pain.
I take pride in how clean our rig is and to roll out the awning and see that makes me sick.