This might help https://www.youtube.com/watch?v=QMcfTzvq9do

Have you tried your lamps? They could be flickering. That happend with me before. Also, I have noticed that Dragonframe as a way of creating it's own light flicker. If you try Eos Utility (The software it comes with) Quite a lot of the time it doesn't have light flicker. (I'm going by what has happened with me before)

I only use old manual Nikkor lenses on my Canon and don't get light flicker. There was a lot of discoution about it at StopMotionAnimation.com back when Corpse Bride came out. On of the nice things about using a Canon with a Nikkor lens on an adapter is the camera cannot adjust the aperture at all. In cameras the camera opens the aperture as much as possible so it's easier to check focus and see the image through the view finder, when the shutter is released it drops the aperture to whatever you have set it at, because it is being and open and closed every frame there can be a small amount of variation.

If you use a manual Nikkor lens with an adapter the camera body has no control over the aperture, and it will stay at whatever you set it out with out moving every time the shutter is released.