This is because of the effect that your pinning / scaling settings are having on your document. The edges of your document define the size of your videos, so if your browser is not the same height and width ratio of your scene, the elements will not perfectly match up when previewed.
I think you’re going to need to either change the distance that your video travels or remove scaling on the video. This technique might work better for you: Proportionally scaling a Tumult Hype document based on the browser width