Hi! Blending mode is Normal. All graphics have clean alpha and are from AE or are text from Premiere. Nothing is covering the graphics. The problem did persist with a garbage matte.
It does look normal after the fade finishes.. unless you play back at a low resolution in Premiere or on Youtube. Then graphics look burnt around the edges and you can see the seam where the video and white matte edges meet.
The only thing that seems to have fixed it (and it’s working perfectly so far!!) is putting the Broadcast Colors effect on the video that has its whites boosted. I think what was happening is that by boosting the whites to get the background white, I was also boosting the video’s luminance and that was bleeding through my graphics. So maybe the broadcast colors effect is limiting the luminance? It’s working and not affecting anything else in the shot so I’m pretty happy for now 🙂