I get this issue a lot. I fix it by moving stuff around, but I'd like to know if there's a permanent solution or I'm doing something wrong.
Details: I'm using MineImator 2.0, each sample taken it becomes more and more opaque.
I have many lights on the ceiling, shadows off (happens when either on or off the same), also still happens in the same direction when I turn off all the lights, sun and turn up object emissive/brightness.
Image of issue posted on Reddit