I had a rack that did that once. It was an old Eclipse rack that had two small screws that could be loosened to adjust the length of the rack. While on a tour with the rack stacked full of crap above my panniers, both screws came loose. One of my riding partners saw the mountain of stuff falling and bolted past me. At first I didn't know what had happened, only that I suddenly had a bit more drag. Mine acted more like an anchor than a drag chute. Thankfully, nothing was lost. I just tightened up the screws, repacked, had a good laugh and set off again.

Also, +1 to the thread lock compound. Since I started using it, I haven't had one shake loose in decades.