I had a similar problem with the jerkiness in the footage. I didn’t notice it until I had made a render and thought it was something in Vegas.
I went back to the original footage right off the card and the problem was still there.
It’s the card. Sometimes even a class 6 isn’t up to the task, but it is very rare.
Here’s the clip in question:
Note when the girl raises her hand to move her hair around the 4 second mark and see if that’s the same thing you had happen.
It was a one time thing for me, and I haven’t had it happen since, but I’m always watching for it.
Just for the record, I’m shooting with a T2i as well and editing in Vegas Platinum 9