Welcome aboard, I always suggest reading this to get the best out of the forum. READ THIS FIRST It is full of tips like editing your profile to show your location because so many answers depend on knowing where in the world you are located. There are many other tips, some may help in flying under the moderators radar.
As far as the bricks cracking, yes because soft fire bricks do not take well to the rapid thermal cycling in a gas forge unless they are K26 bricks. I'm sure the folks who have been designing and building forges for decades will fill in the blanks. To upload pictures you need to resize them by 50% so they won't time out, large pictures take up a lot of bandwidth.