If you have instances (in InstancedStaticMeshComponent or HierarchicalInstancedMesh) with rotation transformations, World Normal is not calculated properly in Raytracing and produces completely incorrect Reflections, Refractions (and even lighting itself if using Pathtracing). This is clearly visible when entering Raytracing Debug → World Normal view. (Compared to Buffers → world normal view which is correct).
It looks like per-instance transformation is ignored when calculating world normal.
It’s also the same in 4.27 preview
I wonder if there is a workaround or a way to fix this somehow relatively easy?