Hi! I'm getting some artifacts in a very simple scene of some grids.
It's two area lights with samples in 4
A environmental light with samples at 4
Render quality 2
I have tried setting all samples up and down, changing the parameters of the grids for more mesh resolution, and always the same errors.

BTW, I am nacho, a very new user with Houdini Indie.

Uncheck preview mode. It'll never look right with mantra. Alternatively, use Karma with the new Solaris lighting context.