Was the meat burned before putting it in the jars?
If anything burnt in a pressure canner, then you'd have to run it out of water. There needs to be a couple inches of water in the pressure canner for the entire time it is processing.
I've pressure canned meat sauces, clam chowder base, stew meat, etc. Never had an issue with burning in the jars. You tube has some good, trusted videos for canning low acid foods. Is it possible some sauce burned on the underside of the lids?