I’m not sure if this will help, but I ran into the same issue and I can give you an idea on what I was able to replicate.
My folder structure was
C:/dev/hab
/BlenderContent for my WIP meshes
/LifeSupport where I created the project
I was exporting the fbx files from Blender into the BlenderContent directory where I was saving the .blend files and related assets. When I imported into UE4 (version 4.9), the import directory was
…/…/…/…/…/…/Dev/hab/Blender Content/StaticMeshes/airlock_test.fbx
And while the “reimport” function seemed to be doing something, nothing would update on the mesh.
From the directory C:\Dev\hab\LifeSupport\Content\FirstPersonBP (where the airlock.uasset file was placed) that path would walk back to the C:\ root, but either way it doesn’t seem to be finding the file for reimport.
Then I tried moving the fbx file into the C:\Dev\hab\LifeSupport\Blender folder so it would be within the project directory structure. When exporting or copying an altered fbx file into that directory, the reimport works fine. The import path was listed as
…/Blender/airlock_test.fbx
Just to make sure it wasn’t because of the space in the “Blender Content” dir name, I created a new folder at C:\dev\hab\test to export to. The import path format was similar (…/…/…/…/…/…/Dev/hab/Test/airlock_test.fbx) and the reimport didn’t work.
Long Story, Short: The reimport function didn’t work when the fbx file I was importing was outside the project root directory, but worked as expected when it was inside the project directory.
Hope this helps.