I had a similar problem on my Palazzo. Turns out the problem was a clogged drain hole but not sure if this is the same on your rig. Slide the window all the way open. Then look carefully along the inside of the track, at the 90 degree angle formed by the bottom of the track and the metal flange running along the exterior of the window. There is a longitudinal slit there that drains the water from the window exterior. You may have to use a wire brush to find it. If the slit is clogged with debris water will accumulate within the track, run under the window slide and overflow into the RV interior. I cleaned out the drain and my window no longer leaks.
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