re:
> Im using the latest beta but I'm using a modified commandbar.htm (it's the one to use the dark scheme I think,
> I forgot exactly, as too much time has passed since I swapped it out)
The modified commandbar.htm is the reason for the error - it's because it's a modified older version and so it's missing something that was added later.
You can add in the missing piece by inserting this:
I think so because the export to FBX needs a newer version of FBX which MoI v4 supports and which MoI v3 doesn't. The FBX import library was updated for v4 and can write newer versions of FBX.
For the build the now import a mess surfaces, but after saving it can be adjusted with switching off the endpoint of each surfaces V and turning on again the endpoint of both direction U and V. only with this tricks you get out a nice surfaces shading. if you have a model without trimmed surfaces you can import right now without problem, only with wrong options.
Hey folks here the work in progress of conversion of my Blender 3d model into 3dm file with Moi3d SubD feature, many crashes and the imports was made with few or single mesh and often the complex shapes are splitted in many object in order to avoid the mess generated surface during import, and the model is made for this workflow. and I also gained experience for better modelling with both application.