I think that happened because of water pump "effect", as in the tight pocket of a safety vest the tin will be often compressed and expanded as you move, thus sucking water in by a little each time. So to fix the problem - stuff the tin really tight and wrap with the tape over the lid too in order to minimize the play of the lid and walls.

Also the Gorilla tape is not really a good option for sealing, as it's not as sticky (gooey) as the regular ducttape (which is really waterproof because its original purpose is to quickly seal leaking pipes).