Sooner or later over time, no matter what the price paid, all fire pans will warp to some degree. Having said the above most will still work just fine.
For some unknown reason tho, when the adult after dinner beverages start flowing and we pile scrap hard wood way up on my hi dollar fire pan supposedly to warm up and the pan turns blood red translucent from the heat, then later on I wake up I find some warping but I know the cause. It is a small price we pay for a good time with friends around a bonfire I think.
I am surprised fire pans last as long as they do.