Rendering effect error

[gladiator-hy]

I have discovered an issue with rendering effect error. There are two parallel planes here, the top one is diffuse material, and the bottom one is conductor material. As shown in the picture, the left part of the upper plane is too bright, but it is diffuse material. I don't know where the problem lies, maybe sample light?
Here is the pbrt files.
pbrt_RenderingEffectError.zip
I'd appreciate any help.

[gladiator-hy]

I have found the reason. There are super large values inside the sky box, when rays hit these, it will too bright. Set "maxcomponentvalue" works.