It happens and as long as they were properly processed and sealed well they are fine.

I find when most jars are first removed from the pressure canner you see them still actively bubbling. That air has to get out. So the pop and resealing is working as it should. The first seal was weak enough to allow the jar to 'burp' yet again. ;)

Why it happens with some and not with all might be due to a bit of difference in how tight the band is screwed on, a smidge difference in the headspace, a bit of broth that got under the lid, perhaps the broth in that particular jar may be a bit thicker or got a bit hotter, takes a bit longer to cool, is sitting in a draft, etc.

Can't say for sure but they are ok either way.

Dave

This just happened to me the other day. I've canned for years but I've never seen anything like this. I was startled to open the pressure canner to find the lids bouncing up and down making quite a racket. I wondered if I'd done something wrong so I'm glad I didn't.

I have a related question. I did my best to skim the fat off the top of the broth but after the jars cooled there is a 1/16 to 1/8 inch of fat of top. Is this acceptable?

BTW this is my first post. I've been reading for years and finally decided to stop lurking. I really appreciate all the wonderful advice and knowledge on here.

Dale