I started recording too late, because before I actually knew where they were, their body, in the prone position, was glitching up and down (up to like 10 feet in the air), much more exaggerated than in the video, so I was able to easily spot exactly where they were before the final circle closed in.

Maybe the glitch occurs when you prone, and then turn, while touching a tree? I think the last game this happened the guy was either behind a tree or a rock too.