I have been working on a mirror that is mostly a sphere and so near to one the conic sometimes switches sign.
DFTFringe will ask you when that happens if you have a conic set other than 0. Once you say yes it will no longer ask you until you restart the program. That usually is a convenience. However in my case there are times I don't want it to invert the wave front but did want it to earlier.
It would be good to have a way to reset that auto invert flag. I have added a way to do that in the tools menu in dalework.
Sorry for more work.
Dale