Corona 1.6 + 3ds Max 2016
I started with this render:
After I decided to rerender floor. I set Render selection: Viewport selection, then selected floor, updated it material (for better understanding I made it with solid color on diffuse) and hit render.
Beauty pass, it's ok:
And alpha:
Enviroment LightSelect element, it's ok too:
Ceiling LightSelect element, it's fine:
Summary, Interactive LightMix element, that should be the mix of two previous elements contains the old floor, from the very first render, that was made before I update my material:
