I screwed up big time

[Bvas]

Just my two cents, but I would have to think it was related to material shrinkage. If it was just a glue line letting go I would expect to see it separate at the end of the piece, not the center.

[buckeyebowhunter]

Brad it was also trying to separate at the ends and not just in the middle. However the middle at the shelf was the worst area.  The ends had just barely started to lift from the core tuff.