I actually done this a few times but only with builds intended for TC. Originally when learning to build for TC I would double check a dry fire on dry cotton to make sure things were good, once or twice they were not and they went up in flames near instantly. One other time I thought I had a good build in while first playing with the Cuboid, the power was up quite high for the preheat punch and the test fire went up in flames pretty quick with wet cotton. Live and learn I guess, never had issues outside of test firing and never with anything other than TC builds that were not right.
Edit: perhaps should be clear, only the cotton wick was up in flames, I am assuming this is what you mean.