Mentioned before in post 1325
With this firebox they mask the real screwup.
Aviationweek, bolding by me.
The battery will also sit on a redesigned frame containing drain holes to allow moisture to escape. In its testing, Vice President and 787 Chief Project Engineer Mike Sinnett says,
Boeing found that moisture paths can lead to short circuits in cells which could lead to “stress in the cell,” or the buildup of heat and venting of vaporized electrolytes.