VFB Source Composite vs LightMix

Can anybody explain to me why there might be a significant difference in lighting/brightness between images when switching image source from rgb to lightmix to composite?
I currently have lightmix and back to beauty REs enabled, in the VFB RGB and lightmix are identical but composite is quite a bit brighter. These are interior shots and the difference seems to be mostly affecting the exterior/environment seen through windows, but it is affecting maybe the GI inside as well. Exterior lighting setup is an a domelight with an overcast hdri, and a vray sun.
Its hard to tell from these images, but just an example. The difference is much more pronounced in other renders.

Thanks.


You might have Affect All channels selected in the V-Ray materials, which could produce some differences.
It’s described at the bottom of this page: V-Ray for 3ds Max
Sending a scene to us would give a better confirmation.​ You could do that from here.