Vertex interpolator (semi-randomly) causes visual artifacts on meshes. This did not happen initially when using or creating this material function but started about 24 hours later but now happens steadily.
This was reported and tested in 4.23.1 (CL-9631420). This was reproduced in 4.24.3 (CL-11590370), 4.25 Preview 7 (CL-12759524), and Main 4.26 (CL-12945139)
Results: The preview mesh's polygons will start to flicker and in some cases the reflection/fresnel won't update properly when VertexInterpolator is used
Expected: Visually behave (near) identical to not using the vertexInterp, no flickering polygons, no reflection/fresnel errors.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-92405 in the post.