QuoteI don't see a difference between 4.4.36 and 4.4.46, but I do see a difference between defered rendering and PT, which strikes me.
Do you mean using the standard renderer with defer atmo/cloud and all shading enabled? I'll have to try that.
I seem to have narrowed it down a bit. It only seems to happen when a bump is applied to the surface, and only with 4.4.46. It happens with both the standard and path traced renderers, though it's more noticeable with the path tracer because (as Ulco mentioned) that normally renders more naturally dark interiors.
Sample renderings attached plus the test file. (Maybe I'm missing something.)
I also tested it in 4.4.44, which behaves the same way as 4.4.45. I don't have any earlier versions installed.