Right now I'm working using an iModel with at least 50 imported SP and SPX files. But one of those imported files can't be updated using the "Synchronize from" option and gives me the following error that says: "Unable to load native file header". I can't find anything on the internet and forums related to this specific problem. Hopefully someone has resolved this exactly situation previously, because the alternative is deleting the existing external data and its model and import again the 3D model in a new SPX file and then create/assign the resources.
Hello Julian,
I will highly advise you to create a service request for this issue.