Sometimes people put JB Weld on them when they crack. I think it is a design flaw with the lack of expansion joints. I have seen many Egg fireboxes that are in multiple pcs, and they still work. BGE will replace them under warranty, and their new ones have expansion joints in them. No idea if those still crack though. I have a Kamado Joe and the fire box has not cracked yet, not saying it wont though, time will tell. I would think after taking it out and putting it back while doing a full cleaning will eventually destroy the cracked and broken ones.
Moral to the story, you could try JB Weld, or apply more pressure on Vision. But if they replace it with one just like you had before cracking, I would guess you will have the same problem again.