The original problem I had was to put an overlay (static image) on a video track. All guides/tutorials I found does this by putting the image into a separate video track. I would prefer attaching the image to the actually video clip instead, but fair enough, it works.
However, when I try to fade out the video + overlay, they do this at different "pace". The video is recorded from gameplay, and I want to cover the chatbox with a black image. It works fine, and I can't see through the image at all. But when I fade out the video track and the image, I can pause in the fading and actually see the chat box. This is extremely frustrating, and not at all what I want of course.
I have tried different things, fading out by dragging the right corner, and a composite level envelope, but it doesn't help. It doesn't matter if it transitions into another video clip or to black, same problem occurs anyway.
Here is an example of how it looks: