gnu, as to the limited area of contact, I would really think there are at least a couple of possibilities that are easy answers. Before the scrunch, when things were in proper shape, that might not mean that all of the blade was prexactly the same distance under the deck surface. So warp things some, and what was already the closest area is now a scrapping area??
Then again, if I saw what was really happening, maybe I would know that that's a stoopid answer...