In the frame of the orbiting station, there is the tidal force, which is proportion to distance from the point where the rope is fixed on the station. But even if he was 100m away, tidal force would be like 7 grams.
So tidal force can't be it. The most likely reason would be some part of the station venting gas out, accelerating. The gas could blow towards the astronaut to make it worse.
Given how fast and loose the movie played with physics in general (orbital mechanics, especially), I wouldn't go too far out of my way to try to explain gaps.
So tidal force can't be it. The most likely reason would be some part of the station venting gas out, accelerating. The gas could blow towards the astronaut to make it worse.