I recently took my TI to Black Canyon on the Colorado River, just south of Hoover Dam (great place!). We started downriver, and sailed 11 miles up the canyon, with good wind. The next day, we took down the mast, peddling with the current. In the afternoon, upriver wind came up so strongly that it was difficult to make headway peddling, even with the current. We put up the mast, and, with the sail deeply reefed, tacked back and forth in the narrow canyon, making somewhat better time, and with less effort than we could do peddling. But, the sailing was pretty hairy, with strong wind, inconsistent in both force and direction (and effects of current). Suddenly, we discovered that the right rear aka had completely disconnected. The brace was still in place, and the tramp held it more or less in position, but the hinge pin (5/16" diameter SS pin in the "knuckle" on which the aka folds) had completely fallen out. Fortunately we did not capsize. After peddling more, with little progress, we dug a 1/4" diam aluminum tent pole out of our gear, and put it in place of the missing pin. This worked for a while, till the tent peg sheared off (my 200 lb mate was out on the tramp). We put the remaining part of the peg (only sheared at top point) in again, bending it to stay, and peddled onward, until we again tried sailing, without putting weight on the tramps, and with the sail even more reefed. This got us back successfully.
The temperatures on this trip were extreme: 110°F (43°C) air (plus very intense sunshine heating everything black to painful temperatures), and 55°F (12°C) water (glad we did not get a long swim, since we were dressed for the air temp). Thermal expansion/contraction may have contributed to loosening the pin.
I have contacted Hobie about this, (they say it is rare...) and I can replace the pin. Apparently (I have not checked this out fully), the pin is held in place with a screw accessed through a cap on a usually-hidden part of the knuckle joint. This is an item I would not have imagined needing in my repair kit, but I will carry a spare or two from now on. When I get part number, I will follow up for those interested. (or maybe Matt will chime in).
I am also thinking about taping around the knuckle, so that the pin cannot simply fall out, as mine did. I am concerned this might contribute to corrosion though, as I sometimes sail in salt water. Inspecting these pins (and the screws holding them in) frequently for any slippage or looseness is probably a good idea.