There's no way that I know of to repair Edison diamond discs when this
starts to happen.  When standard shellac 78s (or 80s, 90s, etc!) warp,
you can put them in a very very slow oven for a brief time, then
carefully weight them down 'til cool to fix the problem.

I tend to check diamond discs very carefully before purchase for any
signs of de-lamination -- it's got to be a really rare title at a
really good price before I'd purchase one!

Jim Canavan
Alexandria, VA