This originally started with a "overdefined" error that showed up on a sketch when it was being inserted into another part, something we do all the time and solves a ton of issues for us that assemblies don't. I went back into the original file to make some simplifications and after trimming out what looked like some unstable relations the whole sketch dropped into undefined. It's fairly complicated so that's certainly a factor but does anyone else have experience with this? I'm fairly sure with some effort I can clear the error but I may have to delete half the sketches relations and rebuild the entire thing.
It may not be so bad. Some times you can get lucky and just delete the right sketch line or relation and you're good. Have you tried this method before? 3 steps right click in the field, go to dialogue box, go to pull down menu and go through each section and see if it helps you identify it.
Good Luck!