That happened to me! Unnerved me enough to turn it off and let it cool down.I could not get the pressure to stabilize. Mine (Presto) has a rubber or silicone seal. It was off set and has not done it since.Move been water bath canning for a few years but I've never pressure canned and want to start. So I bought a used All American and I finally got up enough nerve to put just water in it and try to get it up to pressure. Well the first time I got it up just past 5 lbs and it started leaking a little steam out the side under the lid. Then I put a little olive oil where the lid comes into contact with the pot. Still started to leak at 5 lbs. let it go up to 10 lbs and it was still leaking. Questions are does a little bit of steam coming out the side matter? What are normal sounds for the canner? It was obviously hissing but also making a metal pinging sound every once in a while. Normal? Thanks from a pressure newbie!
I do not think the All Americans have a seal do they? You may want to feel the rims of the pot and lid and see if there are any dips or dings.
I would call All American and get their advice.
It might be an easy fix.