[ContainerTed]

My immediate thought was that you may have tightened the ring too much. The ring should be only "finger snug". You're trying to hold the lid in place so it will have good contact when the pressure and temperature come down. It the lid is too tight, pressure can't equalize between the jar and the inside of the canner.

Also, if you don't let the pressure come off the canner slowly, then the hot glass may not be strong enough to hold the pressure. Usually, the contents will bubble vigorously and you will lose liquid from the jar if you reduce the pressure too quickly. Any slight difference in the thickness of the glass in the jar, or a slight nick can become the weak point that fails.

I would ask if you have experienced any loss of liquid inside your jars when you do your canning, or do you "assist" the reduction of the pressure in the canner.