Here is how to recreate the problem I find often in editing dark footage.

1: Film a total black room.
2: Insert footage into timeline.
3. Select rectangle tool and cover part of footage (as you have to do with filming errors).
4. Fill shape black.
5. Exclaim: "Why is that shape faintly outlined!!"

The black shape has a very fine shape surrounding it that you cannot remove, and worse still when you export to Youtube, the outline is slightly visible which shows up all your filming errors. This does not happen in Premier Elements v10.
Why is this? I have tried all manner of methods to remove it.

I am running very fast computer, Windows 10 Pro, latest version of Premier Pro. High Res screen. Export to H.264 Youtube 1080.

Attached screen grab of problem, but I upped contrast so you can see fine lines on any resolution screen at your end.

There is no stroke or shadow on the shape. The only way to remove the thin white line it is to adjust the brightness of the exported file, but that effects everything else too.

Please fix bug or find work around.