This has happened to three or four of my insert bolts. I just took the insert off, laid it down on something nice and cushy (so it wouldn't get scratched) and scraped off all of the old epoxy from the back side. I then lightly sanded the bolt and the "flower" (that's what I call it anyway) that it is connected to to get the rust off of it, shot it with a little primer to prevent further rust, then after it dried I JB Welded it back down to the insert in the same location as before. It's worked, so far, for a few years, and the only ones that have come up are the ones that are still held down by the original epoxy. The JB Welded ones haven't moved.