dark areas in render

See the attached image. What causes these dark areas? Looks like shadows but appear randomly over the whole image. I can see nothing that would cast a shadow like this.

The error is still there even if I create a new camera.

I render locally (one machine) using progressive. (lightcache/brute).

Max2015 and Vray 3.50.03

Thanks!
K

Ok, found it. Turning off Adaptive lights and using “Full light evaluation” worked. I have no idea why…

I think there was another thread with strange Adaptive artifacts like that.