Here is a Morgan 34 Centerboard diagram. It will help give an idea of how the wire sits in the pendant tube. The tube itself houses the wire, and a packing gland
is on the inside of the boat.
The 90 degree arc
of the top of the board is what allows the pendant wire to always travel in a straight line.
In the event of a failure with this system there are probably only four that are likely.
-The wire could break at the tube (crevice corrosion), or it could break at the pendant swage. A break at the swage could be the result of crevice corrosion
and fatigue: the swage is straight, and the arc
it lays on is curved.
-The pivot pin could let go; how I don't know, but anything is possible.
-The pendant attachment pin could let go; again, I don't know how, since I haven't had a close enough look to know how it is secured.
A good measure to take, although it isn't illustrated, it to drill a half inch hole at the bottom leading edge of the board: in the event of a pendant failure a shackle can be attached there, and a line can be used to haul up the board. A loose board will likely be lost
or damaged in any kind of a rough seaway if it bottoms out.