I’ve managed to get the edge out of the final video now. I also found a slightly better way of explain the problem.
It seems the image mask has a bit of the alpha channel ‘bleeding’ through on the outer pixel of the mask. When this mask was put on top of the text, which was bright it caused the outer pixel to let some of the brightness through.
Here’s my workaround:
I redid the 2nd mask using a copy of the text with a glow so it was bigger, when the opacity was faded up the parts outside the final text are camouflaged in the graphic behind the text.
Not too difficult in the end, but I’m sure it’s not the idea way to do such a task, so still advice and explainations would be great to hear. Why there is there a bit of alpha channel on the outer pixel of an image mask (if that is the case)? Where else could the edge of the the mask?
Cheers