If the windows are sliders, that's the way it's designed to work. Yours _may_ be leaking more than usual, tho'. Be sure the lower slide track or channel is centered, with equal gaps at each end between channel and frame. That's what allows the water to drain down to the weep holes and out.
We (the factory & I ) looked & looked for a small leak that I had in the overcab bunk. The mattress kept getting damp in one front corner. Looked, applied sealer to the roof-side joint, still leaked, looked more, more sealer, damp again.
I _finally_ found it. Turned out that the slide channel in one window had moved to the front blocking that drain path to the weep holes. At home, I was parking ever-so-slightly nose down, so water accumulated and dripped out, to the inside. Took less than 30 seconds to fix.
Jim, "Mo' coffee!"
