Double post from me but I had to so you could see this.
A few days ago I tried to help out in Harmy's thread by analyzing Obi-Wan and Vader's duel. A couple days ago when I got an encode from DJ of our GOUT SW I decided to watch the duel a bit in the same way, looking closely at stuff and that's when I noticed something interesting in how they have combined the shots into this scene.
This shot comes before Vader hits the wall with his saber, yet the crack is already there! It's also a mirrored shot which can be seen if looking closely at the panel on Vader's armor:

Then, when Vader is about to hit the wall, the crack is once again there before he hits, but now the image isn't mirrored anymore:

Next shot, the crack starts burning, the image is not mirrored:

In this shot we have the same angle as in the first pic except it's not mirrored anymore, but look at the crack in the wall. It's a different crack this time:

And now the old crack is back:
