Can be the way those tuflight job boards are snapping by wave pressure . In that kind of construction there is not enough glass linking.
This link i'm talking about is made by glass overlaps normally done in laminating job.
The board is cracking under effort like a beam fractures you can see on video is running along the rail is on "neutral axe" so called in physical term, the two halves ( deck and board bottom) of materials sliding opposite of each others.(Deck side in a compression way and bottom side in extension way orreverse case)Fractures in deck or bottom or the one cross the rail are glue joints between sheets of material.
http://en.wikipedia.org/wiki/Three_point_flexural_test,Can happens on any brand in that kind of composites construction.Don't blame Naish brand