Galley Hatch Wood Cross Bar Separating

I have noticed the two center cross bars / supports have both developed gaps between the ceiling wood panel and the solid lumber horizontal cross bars or supports in the center.
I imagine an adhesive was used in addition to the 4 screws that attach each cross rail to the vertical end supports. The center of the cross bars are bowing down in the centers. I am looking for suggestions as to why this might be happening and the best method of repair.

 

Build photo.

 

How are the soid lumber cross members in the middle of the galley hatch attached?

 

Thank you, and yes, that is what I was thinking as well. However, I have not found any glue residue between the panels and cross bars. This is a 2009 unit and so I am surprised it would only be appearing now, unless we exposed the camper to an unusual environmental condition that may have caused this. I also wonder if it could be a humidity thing sense it has been in arid Colorado since 2009, and now lives in the Great Lakes Region. Maybe it will shrink back tight this winter.