UE4 is using mesh’s tangent space to calculate reflections.
If your mesh has a high normal gradient on flat surfaces, it will be visible.
To combat this, you might want to place hard edges, where applicable, to keep flat surfaces flat, or add additional support edge loops to still keep the mesh smooth, but at least reduce the gradient on flat faces.
Hi there 
i have encountered an odd error in the reflection (cube and sphere) of my counter-mesh… if i import the mesh as i always do the flow of the surface is just right but the reflection is tilted/distorted… cutting the phongshading in cinema4D seems to help and set the reflection straight again, but then i get a noticeable cut on the transition from the flat part to curvy edge 
letting ue4 compute the normals during import helps to in regard to the reflection, but dismisses the phong completely
hopefully someone knows a solution for this 
i am using cinema4D r18 (tried r17 too, but no change) and tried all fbx-export version from 2010 through 2015.
The Project uses forward shading because its a VR-Project (does that matter?)
Hi , thanks for your answer, but the gradient wasn´t the problem (i had already checked that in cinema). But i found the problem
The distortion occurred with this mesh, i had the fbx-export set on triangulate at export…
with this mesh the reflection is no longer distorted, i had to export the mesh with quads and then ue4 converted them itself, now everything is just as its supposed to be! ^^
maybe someone with the same problem finds this and i can spare them the detective work xD
don´t export with triangulated geometry! 