My best guess is that, there may be 2nd piece of metal right underneath the roof, and those upside down hex bolts were welded on the 2nd layer, so if they didn't make a good seal around the thread, water will leaks to the inside. I am not sure if this make sense, but if you look at the leaking area, you see 2 layers of metal combines together(The place I circled in Yellow). It's gonna rain for the next couple days, and I clean the water spot after I sealed it, if I don't see any water spot in the end of this week, we can cheer!Wow very interesting. So this might have been purely coincidental after all. If my perspective of directions is correct, the photo showing the water intruding between two panels is looking toward the front of the car and makes me wonder why, given the direction of water flow, they lapped the top panel UNDER the right panel. If you think about general waterproofing practices for say.. roofing and siding.. top down you lap the higher panel OVER the lower panels. And whatever they're using to seal the seam has a high face, so I guess it's a tiny retaining wall and a point of entry. In addition to the welded post/threads, I was thinking maybe there's some pinholes in this. And oh boy that Odyssey guy really went all out with that silicone lol
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But your experience has me wondering now. I usually hear dripping water near my b-pillar when it rains but I never see wet interior trim, so I haven't chased it yet. I'm guessing I may have something similar, but it may be dripping all the way down to somewhere i can't see and just doesn't affect my trim.