So I was working on the modular floor asset pictured above and in UE I was having a very strange problem. The triangular face in the center would appear transparent and show the face on the other side of the mesh. At first, I thought this was an incorrect face normal but it wasn’t.
The weird thing was only part of the face was transparent, not the entire face. Another weird thing was; as I moved the camera around the transparent area would follow me. I googled for an answer but all I found was “check your normals” and “make your material 2 sided” which didn’t help.
The solution: my materials blend mode was set to translucent instead of opaque.
So many hours spent googling instead of modelling. Anyways just putting this here in case, somebody else does this.