Water leak

I don't know how yours is built but my 2003 Pace Arrow 37 ft had a leak in the bedroom similar to what you describe. I checked every where roof slide seals etc, No water lines anywhere near the leak. I had a trim strip running down the side of the coach right where the side walls and floor meet. It had the standard caulk behind it and being 10 years old it was not in good shape. My RV repair shop said to remove the strip would bend and crimp it. It was painted to match the paint body stripes. We were going to get a heavy rain so on a hunch I put duct tape over the trim strip and no leak. (don't leave tape on too long) I don't use silicone but found a clear sealer at Lowes that sticks even when damp. I masked the strip and body used a caulk gun and mineral sprits to smooth. I took several hours to do the whole side but looked good. Two years later still no leak.