Toodie, any through-hull hole is suspect. Water can run a very long distance in a trailer before it hits a spot where it can drip. I had a leak in my '02 Scamp
from the escape
hatch on the top. As it turned out, three of the screws had silicone that hadn't properly sealed the screwhead and it allowed water to leak in. Fortunately for me, I was inside and could see where it was dripping from and follow it back. It was interesting finding the actual leak tho!
So, it could be the top seal on the door, it could be a vent, fantastic fan, air conditioner, clogged window weep holes, or just a rivet or screw that isn't well sealed.
Anyway, a reputable RV dealer will figure it out for you.