A grub screw is a type of set screw that has no head. It looks a bit like the larvae after which it is presumably named.
My understanding is that Sea Wisdom's "structural shelf for top bearing" detached from under the deck (ref the article's drawing) allowing the rudder bearings and tube to drop down out of place. The plywood and fiberglass structure was replaced with a metal structure but apparently this didn't completely solve the problem. I notice she's back in the water at KKMI so hopefully Will will be able to sail her again soon.