Workbench .iam assembly to step conversion download

When I upload a .iam step file with all the .ipt parts to grabcad workbench and download the assembly as a .step file it appears to be empty when I open it.
The individual parts I can convert to step without a problem. Is there anyway to also get it to work for the assemblies?

I'm asking this because of the upcoming fusion 360 hobbyists changes where the export .step function will be removed but you can still export .ipt and .iam's so I'm not actually using inventor but the .iam file appears to be correct in the browser so I don't think this is the problem