Hmmmm... watching the second goblet video, you lose lumbar control on a couple of reps.
Looking back at the video (for the third time! /nohomo) and you're rounding your upper back. I'm guessing this is because of how you're holding the dumbell, but I've noticed from front squatting how this really translates down into the lumber region.
When holding the 'goblet' really pin your shoulders back and force your elbows up, back and in as you do this. This will put you in a more vertical position and really push your ankles to accommodate.