I just tried canning another batch of broth and had another jar explode. I actually think there's something wrong with these 1L jars. The pressure canner hadn't even come to a boil yet; it was just coming up to temperature when I heard a loud "bang!". I opened it up, since no pressure had built yet, and sure enough, one of the jars had the bottom blown out of it. Looks like this must have been a bad batch of jars, or something. Really weird. I'm pretty sick of wasting bone broth at this point, so I'll probably just toss the rest of the jars or use them for non-pressurized storage. What a waste :(