Maxxair Fan Still Leaking?

Hey everyone! First post here. I was hoping someone could shed some light on why I’m still having some water leakage after heavy rains. I’ve sealed the Maxxair fan on the exterior top of the fan twice now and it looks super water tight. In fact no water drips into the inside of the van while it’s raining and the van is parked.

However I’ve noticed when I drive the van after a heavy rain I get some moderate dripping while the van is in motion. As you can see in the picture it’s not a ton. My thoughts are maybe there is water getting in through the side openings on the top of the fan (the natural openings that you can’t seal) especially if it rains sideways.

Maybe there is a pocket where water is getting trapped and then when the van moves it leaks out? If this is the case I’m hesitant to seal it anymore on the inside because then I’ll just be trapping the water that shouldn’t even be getting in in the first place. I hope this makes sense and I hope someone has some insight lol Let me know if you need more pics of clarification.