After watching the film some more, I've reached the conclusion that my deadlift form was quite bad.
My hips are simply too high.
Here's where I begin the pull on my first rep of the first set (one of my worst reps):
Here's where I begin the pull on my first rep of the second set (one of my best reps):
I would still like to get my hips a bit lower. Going forward, I'm going to work on locking my lats and sitting back more into the pull.