I was out sailing in very variable winds today- mostly about 6 knots with sustained gusts probably to 15. I was on a port tack, barreling along in a gust and happened to look over to see my starboard shroud dangling free. The bolt part was gone and the shackle part was just hanging. Luckily I noticed it before tacking! Also, luckily, I had another person with me, so he held the tack while I looked around for a fix. Third luck was I had a single loose bolt in my odds and ends which turned out to be the right size and thread. Threaded it in and off we went. Fourth luck was when we got back to the dock, I looked down on the cabin top and there was the missing bolt, laying up along the halyard. How it stayed there I do not know.
Anyway, I realize now I should probably wire those shackles - the bolt part does have a hole. Is that the common practice?
Meanwhile - check your shackles!