This topic about another problem.
Problem with shading solves when Environment Light Cache is turned off
I'm looking into the problem.
As a reminder this should be put in the tooltips of clamping. ""Too low value can break lighting and create artifacts with GI cache """Fu*k, this scene was driving me crazy, I was getting out all kind non sense results.
I'm not sure to understand the statement but I have the feeling you have to run the rendering without clamping to get a valid suggested value.