This video tells all, I used a reflection shader on this patch, and this is what happens. The reflection shader works perfectly on flat surfaces.

http://www.youtube.com/watch?v=lwuCJtU6 ... annel_page

I made a waterfall and noticed the same problem. I'll see if I can record it and upload it later.

Use -patchmeta in order to turn a NURBS patch into a set of flat surfaces.

You should not use reflection shaders on surfaces with many vertices, including patches. And you really MUST not use them on nonplanar surfaces as that will kill fps.

And this is caused by reflection vis culling being done slightly wrong. Cannot be avoided, and normally has no huge impact (if you keep your reflection planes small enough).