My 2019 330RSTS had a water leak in that area. Thought my storage door was leaking, resealed and still leaky. Looked at all the seals around the cap and roof, nothing. Took apart the closet and found it was coming from outside sprayer water line. We were on the road when I figured it out and ended up cutting the line and installing a sharkbite cap. No more leak.
This spring I found the PEX tubing to threaded fitting at the outside wall was not sealing. I found a suitable replacement fitting at Menards and it's totally dry now. The challenge was that it barely leaked because it was mostly airlocked before we used the sprayer. Once we started using the outside sprayer, it leaked pretty heavily.
2000 FR Flagstaff 625D - Sold
2013 White Hawk 30DSRE - Sold
2019 Eagle 330RSTS
2020 F350 Lariat 6.7L powerstroke, Rapid Red with Lariat Sport