I have a big problem on creo. Since this morning, it is impossible to modify my assembly. The crash software has every manipulation and I still have the same error message. (see picture)
I would suggest submitting a support ticket to PTC for traceback errors.
Other suggestions is to try opening the parts and sub assemblies to see if you can find something corrupted. If you are using Windchill, try adding the assembly to a new workspace, sometimes workspaces corrupt.