Water leak, we cannot find.

There is a recall on some models. Apparently water laying in the coroplast "membrane" can cause electrical issues because of the way trailers are manufactured. These trailers and probably most other brands have all the electrical and plumbing just laying loose and supported by the coroplast "membrane" thus nothing is tied to the frame or structure!!! If that fills with water you can have major electrical issues and possibly even danger because all that stuff could be laying in water. Water can actually be forced in or find it's way in between the screws holding up the coroplast!! Imagine the pressure especially in the front when traveling in heavy rain at 60 MPH. Water will come in and lay in the lowest point causing it to sag even more with the weight of water!! Check with Grand Design to find if your unit has the recall. They may take care of this for you.

I agree with one post that suggested you drill holes in the lowest point of the coroplast to let water out before removing any screws yourself!! It could be very heavy and fall when the last screw is removed.