I've never had a limb bolt snap, but I never backed off two turns without backing off the other bolt two turns as well. If you screwed one all the way out and left the other all the way in, hell yeah somethings gonna break! There was definitely a wrong way to do it.

What happened to me was getting a pretty bruised wrist when I wanted to change the strings and cables on a Darton Lightning and did the time honored back out the limb bolts routine. The bolt cleared the hole and the limb butt nailed me. It was still under considerable tension. I had to box up the pieces and take it to the shop to get my bow put back together. That's how/when I learned they'd made it so you couldn't do that any more.

I think it's a shame that crossbows are also like that, especially considering how hard it is in a great many areas to find a shop that will work on them... or even let you in the door with one.