I think that is what happened to me a few years ago, though only to one of a 3 pack of C6-0 engines. I was attempting to launch my original Centuri Alien Scoutship Flying Saucer that I built when I was a kid at my son's Cub Scout launch. The cato in my case was more of a zero-thrust, slow molten burning fuel dripping out of the bottom of the crumbled nozzle on the pad and ground which singed the cardstock saucer rocket a little before all the fuel burned itself out. I had stored that pack in my garage and it had gone through a few extreme seasonal temperature changes.