Must join 52 in the "I'm no expert" category, but will offer an opinion anyway, cause that's what we do best around here!   :snoopy:

It is always possible that your seals were defective, a bit too old, or for some other reason did not make a good seal.  We all have that happen occasionally due to some imperfection we can't see, but in the case of the mass failure of an entire (or most of a) batch of something, there is obviously something more than a fluke going on.

I once forgot to get the seals into hot water soaking until everything else was ready to go, so the first couple of jars had seals which had not been warmed very long.  Sure enough, those were the jars which didn't seal very well and ended up in the refrigerator to be eaten quickly.  Other times when I didn't get the seals into water for as long as I'd have like for them to warm everything worked just fine.  Who knows whether it was the seals themselves (being brand new ones in those cases), the temperature of the kitchen, or the phase of the moon!

Another thing I've noticed is how carefully I must wipe the jars prior to putting on the seals depending on what is going into the jars.  Things that I use clearjel in, for instance, seem to be really sticky on the jar rim.  And when canning anything with a high fat content, I must use a dry cloth to get all remnants of the food product cleaned from the rim as well as a damp cloth.

It's an interesting learning curve for sure!  Some things seems to remain a mystery for which there is no explanation.  There are some very expert canners among us here who will be able to give you much better advice than this explanation, but these are a couple of things to get you thinking about the possibilities.

How much headspace did you leave?  And were the jars covered with water??  Sometimes if the bands are on too tight, air cannot escape the jar, but you probably already know that!

Also, if you tighten the bands after taking the jars out of the water bath, that also interfers with the sealing process.  Leaving the bands on after the 24-hour cool down phase can keep the seals on tight enough to appear to be sealed when they are not, assuming the seal wasn't quite right in the first place.

We are pretty much all being led, some of us kicking and screaming, into the "Take the bands off!" prior to storage camp!

From everything I've read, if the water doesn't completely cover the jars by at least an inch or more (I always go for at least 2-3 inches, just to be safe in case too much water evaporates) of the boiling water there is no way that the contents of the jars, especially ones which have contents which are not already hot to begin with, can reach a high enough temp to kill all the bacteria.

Not trying to insult you here, because you sound like you have experience as a canner, but it pays for all of us to review the elementary stuff from time to time.  Suzanne has a great tutorial on the basics.  http://suzannemcminn.com/blog/…..th-method/ and another on using a pressure canner http://suzannemcminn.com/blog/…..re-method/

Please take no offense at my suggesting reading through Suzanne's instructions, especially since I am a beginner myself.  I know that I know all that basic stuff, but look over it again and again just to make sure I don't forget the important things.  Also, when you get as old as I am, I realize that I forget an awful lot of simple stuff, even things I've done for years!

Good luck with your other jars.  I sure hope they are all right because it is so heart breaking to go to all that work then have a seal failure.  But, this is a great place to come for ideas and encouragement.  These are the gals that got me back into canning again after not having considered doing it for decades.  Then I discovered that ALL the rules had changed!  But, much more is known now about food safety than when I was a little girl, so it really pays to check out the new ways of doing things.

Hang in there!

So glad you took my comments in the spirit they were intended.  

Our Cindy posted a recipe which sounds basically like what you were canning.  It's over in the pie recipes.  She said she has done this particular recipe at least two years now and has had great success with it.  As I recall, she used 3/4 inch head space.  Maybe that could be part of the problem?  I have had a couple of times where the contents have bubbled out of a jar or two, which naturally made a proper seal impossible.

Meanwhile, it's good to have another canner in the group.  I'm trying to catch up with all you experienced canners, and have learned a bunch from everyone here.  We've had a lot of fun with a few of the recipes, like Suzanne's Caramel Apple Jam and Dede's infamous Hot Pepper Butter.  Looking forward to trying some of yours, too.