Hi Hazel, water is crazy stuff. I am going to say that is more likely the angle of the rain than the quantity of the rain that is causing your leak. Does it leak if you are driving in the rain or only when you are parked?
I used to be an apartment manager and we had a window that would only leak when the wind was very strong from the South. It would soak the landing carpet, but we could never find that leak.
Being a small trailer you will find the leak. Try a garden hose at different angles and see what happens. Don't forget the belly band. Good luck.
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