My wife called and said one of the four fire bricks was cracked, and now in two pieces. It now won't say in place. She asked should she run the stove without one brick. I said lets not. Told her to replace all four. I know there are different materials used for these. I'm assuming they all will work, Any reason they won't work and I should look for the exact ones I have? What do you think about running without one of the bricks?