Short description of error
First, sorry if this report is a duplicate, i've found some similar report but could not make sure they're the same.
A few bones orientation are wrong when exported to Fbx then imported in Unity or Unreal Engine. Importing back the Fbx in Blender is ok, but not in these game engines.
Exact steps for others to reproduce the error
-Import the attached fbx file in Blender, then check it's ok.
-Export it to fbx using the default options
-Import in Unity or Unreal Engine. The lips, cheeks and chin bones are distorted. After investigation, moving of +/-0.01 the bones transforms in Blender before exporting can fix it. So it seems to be an imprecision error at some point...