The issue still persists in UE version 4.10.4 but we found a work-around until it is fixed (this information may also help engineers to find the source of the bug).
The work-around is quite simple:
- Open the uasset editor.
- Scroll down to “Import Settings”.
- Expand the “Show Advanced” options.
- Disable “Build Adjacency Buffer”.
- Save the uasset.
- Reimport at will!
This worked out for us but we also found out that everyone working with those assets needed to perform this work-around manipulation otherwise the assets don’t update properly through versioning software (Git, Perforce, etc).
Alexandre Zenga