Fade out starts before 1st Keyframe

I have the issue where I set two Opacity keyframes with 1 at 100% and one at 0% (fade-out)

However, as you can see in the image preview, the video has already faded out almost completely and it has not passed the first keyframe yet.

When I remove both keyframe points the opacity stays at 100% and the clip plays as it should, when I re-add them again, same problem... It goes to 0% before passing the first keyframe...
This proves there is nothing wrong with the clip, and the clip has got content.

I first thought it was just a preview issue but it was also in the exported file

Does anyone know why it already finished the fade-out to 100% without passing the first keyframe?