I have an issue that occurs after importing a STEP file, saving it as an assembly, closing the assembly, and then reopening the assembly. Parts that were previously fine are now suppressed and I cannot unsuppress them. I can, however, open them so it's not a matter of SW not being able to find the file.

Each suppressed part has a yellow error triangle next to its name in the assembly tree. The error message reads either "the file for this component has a non-matching internal ID" or "Error opening file."

What would cause this? When I import the STEP file, the assembly appears fine. It's only after saving it as an assembly, closing it, and reopening it that this problem occurs.

I'm using SW2018 SP2.0.