Recently I watched a video on YouTube by Scott Manley: How To Do A Hoverslam - Things Kerbal Space Program Doesn't Teach. It deals about landing burns of Falcon 9 first stages. It features short clips of stage actually moving on barge left and right. To illustrate I provide links to video at relevant times:
The first stage moves on the barge and I was trying to determine the cause. The captions say it is May 2016 landing. I checked the Falcon 9 launches and there were 2 launches in May. May 6th was a night landing, so we can rule that out and May 27th. I tried to find other videos of these landings but none show this movement. I thought of bad weather and high seas of being the cause of this movement, but... the barge does not list enough for rocket to skid and also I think It would tip over before sliding. In some moments it looks like it almost lifts up a bit. My other guess is that the rocket is already suspended on a crane. But I have found no video evidence. Can somebody with a bit more insight explain this movement?