I have had the same thing happen to me. I was camped at Crabtree Meadows in a hard rainstorm. I set my BV-450 out in an open area, upright and completely closed. When I got breakfast out of it the next morning there was about 1/4" of free water in the bottom of the canister. I couldn't explain it then and I can't explain it now. The way the lid on the BV is configured water would have had to flow uphill through the threads about 1-1\2" to enter the canister. I put a plastic bag over the BV now if it looks like rain.

I have also had water get into my Bearikade Weekender in rainstorms. It appears to get in around the fasteners and can do so in some quantity. Now, when I put the Weekender out I position it top down. It seems to work.
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May I walk in beauty.