Thanks so much for taking a look Chosker. Unfortunately, changing the translucency sorting priority (of both the square and the decal, tried going both positive and negative) didn’t change anything. For measuring pixel depth and target depth, I guess I meant destination depth and pixel depth.
In another forum, someone recommended that I try RenderDoc. I checked that out briefly. Maybe I’ll come back to it. Unfortunately, on my current timeline I think I’ll just have to move on and maybe come back to this later.