From what I can tell, and I think you can see a bit in the video, when the grid fins ran out of hydraulic pressure they locked full in one direction. The last

From what I can tell, and I think you can see a bit in the video, when the grid fins ran out of hydraulic pressure they locked full in one direction. The last burn this thing does is often called a 'suicide burn' as there are a couple complications to landing it. First, it only has enough fuel left for a short burn. Second, it's not possible to run the single engine they use to land it at a low enough thrust level that it can hover. i.e. 1 of 9 engines at the lowest possible thrust it can operate at is more than enough to accelerate the empty stage body upward. As a result they have to 'blip' it just before landing and cut at the exact time needed to reach 0-ish velocity at landing. This means the thing is moving _fast_ just before the video starts. I'm guessing that with the grid fins locked in an extreme direction 24 seconds before getting to the barge they still had a lot of influence over the flight path since it was still moving fast. This pulled the top to an angle. The engine fired and the vectoring capability of the engine tried to toss it back over the ship but it just couldn't correct the lean before hitting the barge.