Notes from FB comments:

For Vaders saber in the cave, just listen to the scene. His sabre is heard igniting but it is already lit in that shot, so you now see it ignite. The hangar shot hasn't had the ceiling replaced yet ( you can still see where the set ends). This will be replaced once i have built and filmed the new hangar miniature.

the blade in the original was not only attached in the wrong place, but also bent. You can see here that the new rotoscoped blade is correct:

http://screenshotcomparison.com/comparison/89625