[MITCHELL]

I have been canning since the albacore were a yearly thing off San Diego coast. And I can say I probably had at least half a dozen jars crack over the years. Maybe because I reuse my jars, until they crack. I always try to keep the heat down as low as possible. Just a slow hiss and steady rocking on the pressure weight.
But I have never thrown out the fish because of a cracked jar, it's always a clean crack and the fish comes out in one big chunk or you have to separate it to get out of the jar throat. When I say clean crack that's means no chips of glass. And of course I examine the fish looking for any glass. I eat the fish right away don't serve anybody. Anybody that reads this can make your own opinion rather to eat fish or not but I don't ever remember removing a glass chip from fish. If you have never canned your pretty much clueless.