I have found a solution(ish) for me. It seems some plugins are unable to be used in Scaler and may be the source of the issue. In my case, Usynth and Khords can’t be imported. On my first import, everything seemed to be fine, but every subsequent import produced the Error 2 message.
In C:\ProgramData\Scaler Music\Scaler 3, I deleted plugins64.cache, plugins64.log, and plugins64.ignore. I could then run the import again and pick up some newly installed plugins that were getting blocked by the error. The incompatible plugins still don’t get imported, but I guess that’s just life.