I keep having this problem when importing my meshes. I simulated the cloth in Marvellous Designer, and imported it into 3D Studio Max and then exported the whole model into UE4 as an FBX. All of the pieces of the model work fine except for one of the sides of the duvet. I thought it was that the normals were flipped but then after trying to correct it in 3DSMax I still have this result.
Hi Mafyoc,
Looking at your image it does appear that the normals are flipped.
You can check this in the editor by opening the mesh in the mesh editor. In the toolbar select the button that says “Normals.” This should give you an idea if the normals are facing correctly or not.
Feel free to post any additional screens shots and I can try to assist. If that’s not helpful you can always post a link to the FBX here or if you want to send privately you can send a link to me via the forums in a private message and I can have a direct look at it.
Thank you!
Tim
Thanks for the reply. It turns out I hadn’t flipped the normals when I simulated the mesh in Marvelous Designer, which caused this when importing the mesh into UE4.
No problem! Glad it’s resolved! 
Tim