It looks like this stabby-tip was built without a layer of foam beneath the blue marine (Ensolite-like) foam, and only had a piece of it taped to the core and folded over, causing it to fail. I hot-glued a piece of leather to the core, barged a layer of foam, then barged a 0.5" Ensolite as a test (I think it's too thin of a layer to do anything).