[Crex]

I agree with WBE on this one.
Do have a question w/suggestion - try placing two blades in side by side, one edge up and on edge down. If they both warp in same direction then it's most likely heating element differential. I have always blamed severe warping as a failure on my part to make sure all is "even" prior to HTng. Minor warpage does occur frequently with O1 and the thinner the cross section the more likely it is, for me. Just can't see it being the steel if you have run stress relief cycles.

Since I forge all my blades I have made it an automatic practice to stress-relieve each blade both after final forging and after final profiling. Maybe more habit than necessary for most forgable steels, but not a big issue as part of the process time wise and I don't have to step back and wonder if I did or didn't...it's always did.