How many times has it happened to you? You have a part constrained in an assembly, then you (or someone else) adds a fillet or chamfer to an edge, now there are constraint errors when you open the assembly "Relationship with Undefined Geometry".
I get that the edge that was being used is no longer available, but with a mature product like Inventor, it should be able replace that edge with the new one created by the chamfer or fillet.
Thanks