Hi,
Degenerate Tangents simply means that you’ve got a UV that is not setup correctly. This could be simple UV stretched face that is causing the issue.
You can read a little more about it here in this post: Degenerate Tangent Bases - Rendering - Epic Developer Community Forums
In 4.7 MikkTSpace tangent basis was added to the engine. Any tangents that do not align with this will kick back the degenerate tangent error. The warning message could use some tweaking to better reflect this as a UV mapping issue though. In 4.8 you’ll still get the same error message with any assets that do not have UV mapping that falls in line with the MikkTSpace method, but you’ll have the option to disable MikkTSpace in the Static Mesh Editors build settings to use the method that was set before 4.7 was released.
I hope this helps.
Tim