Hi,  I have come across a rebuild bug. I have an assembly with 3 parts and 1 subassembly. No external references between affected parts, except for mates. When I open a sketch in the part of the upper assembly, making no changes, an unrelated part fails in my subassembly. It has a sketch in it which drops the plane to which it was defined. This happens everytime regardless if I go through, reassign, and rebuild the model, umteenth time now :-(