I've been trying to work around this very annoying bug, while working with SolidWorks to get it fixed.

1. I import an assembly from a STEP file
2. I then call ModelDocExtension.SaveAs(silent+references). Everything is fine up to this point. My parts have 28 custom properties.
3. I set a few custom properties, rename the component or set a material in the parts. It doesn't seem to matter what I do here.
4. I call ModelDoc.Save3(silent+references) or click save in the UI with references.
5. Now all my parts lose all of their custom properties. The list is completely empty

Does anyone know a way to save an assembly with references without using Save3?

I am working with SW2020 SP4, so there are no updates to run.