Background image not rendering correctly

When I import an image, I scale and place it perfectly, the problem comes when I render the video. The image automaticly moves down, I've tried changing the position so many times and it still appears in the wrong position in the video, so I suppose that it's a bug. Here you have an example, where the image moves down, leaving an anoying black space at the top. Oh, and also when the video begins, it appears without the correct scale for a moment, and the it places wrongly.