Hi @anorrback - I’ve had a look. It seems the issue was with the helical sweeping operation on Part 2. I’ve suppressed this and now the importing works. (I also removed the TA etching, but checked and I don’t think that this was causing any problems)
You can see the project on SimScale here: https://www.simscale.com/workbench/?pid=1902942346300798850
And the Onshape modifications here: https://cad.onshape.com/documents/56af27e0e4b07682577e1cdd/w/11c6dc46c9da0313fddf0fcd/e/567fcdaa5161f8b8f7a5b8f0
Why this helical sweep is creating problems - I am not sure at the moment? I will take a deeper look into this.