I’m having this problem for a long time now and I’m still unable to solve it. Please check the image below. Why do I get these “phantom” rays around the rays that the sun produces? These surely don’t appear there in the real world, do they? It looks like there are 2-3 suns casting rays instead of 1. 
Another long standing issue is that sometimes there’s abrupt cut-off of the rays, as described by me in this older thread but I think you are already aware of it. Hopefully it’s going to be addressed at some point. 
These lens effects stuff are pretty important to my workflow since I often work on events jobs where there are light sources such as spotlights and other light fixtures which are crucial to be presented as accurately as possible. So far I’m able to produce very decent results with Vray’s lens effects but I think there’s a little room for improvement.
