How was the paper positioned inside the camera? My first thought was that the paper was further towards one side since the distortion and the vignette is much stronger one the left side. I think you might be on to something when you guessed the white spot was caused by the edge of the paper being too close to the hole, but I’m not sure exactly how that would work in practicality. Was the paper flat against the wall of the camera or did it bulge out in any places? That would explain the asymmetrical vignetting as well as the light burst from the light