The culprit is the mat stick on the trunk lit. They stick it out of place and cause the rubber around the trunk contact with the mat rather than the lit metal. Try to observe it, the water is come in from top.

I suffered this before, i told the SC thats the culprit, but they said is rubber problem. Nvm, free new rubber, they want to change let them change, after change i fix the mat by myself. Water proof now.