One thing I noticed in examining the temper ruined razor I spoke of is that pressing the damaged edge portion of that razor head on and perpendicular to the edge of my thumbnail showed that my thumbnail easily pressed into the edge damaging it. Crumbly is the best descriptor. I corroded edge that apparently can appear to be normal I would think would NOT yield so easily to a fingernail, etc. On a corroded edge that "good" steel is still tempered. You may want to try, under low magnification, pressing the edge into something like a pin in an area known to have given you problems. I would argue that if anywhere along that area, the edge crumbles, I don't think corrosion is the problem with this razor. Just a guess.

Chris L