Exported FBX file contains no mesh data

Im having a strange issue when exporting a mesh. Specifically a mesh with alpha plane fur (around 5k tris total).

When I export the mesh to FBX 6.1 (ASCII so its human readable), the file only has basic information about the mesh but no vertex information.

Importing it into UE4 obviously fails since theres no mesh data.

Any ideas why having a lot of individiual meshes like that cause this issue and is there a work around?

Note: Exporting the mesh without the alpha planes works fine. Which makes me think its something to do with the number of individual meshes within the main object.

Ok I found a work around. I just created a new file and appended the object.
It exports fine now.

I realised it might be related to the file when I noticed the following error in the console:
“Error, region type 2 missing in -n name: ‘File’, id:5”

No idea what it means but creating a new file seems to solve the issue.