Why is part of my geometry missing

HI Folks: This is a datasmith import of a blender model -- its properly unwrapped and modifiers applied -- can someone please explain why a bunch of geometry is missing?

Hello ,

At this time, we don't have an official plugin for Datasmith and Blender, so I am assuming you used a third-party plugin to create the .udatasmith export to import into Twinmotion. It is possible that this could be a bug with the plugin, or the plugin requires specific conditions for the export to function as desired. Unfortunately, we cannot provide official support for this, since we have not developed or maintained the tool you're using, so you may need to contact the tool's developers for assistance.

Best,

​​​​​​​Raghib