Warped Cast Iron Clamping Flange ????

This is a follow up on my leaking flange/ shower pan liner situation. Aside from the tile guy using Henry 208 for sealing the pan around the drain which I have learned may be a mistake, I now notice when I take the flange up and look at it that it is warped! It is cast iron. I did not realize that cast iron warps. this warpage could have been contributing to the leakage and deterioration of the seal. Well, what do I do. In theory if it is warped, it has probably conformed to the flange below that is also warped??? If I put on a new clamping flange it will then not be plumb to the flange underneath I think. I could try to figure out where the compatable warpage is and line it up but that may be impossible. What to do? Does it make sense to change out just the clamping flange or does the flange down below that connects into the drain have to be changed also. If so, it means busting up a concrete slab. HELP :-)