[Cin] Fade black flash

[Camille Harang]

Hello, when I put a fade in the title video effect (here the white
"Hello" text https://www.youtube.com/watch?v=dJLj0w6NUSo) you can see
that letters appears as a black flash briefly in the first few frames,
then goes back to transparent, then the fade starts normally with the
white color. Does anyone know how to fix this? I have the same problem
when using transparent PNG images with fade video transitions, first
black, then normal transparency.

Thank you very much,

Bests,

Camille.