Judging from the hint in the guide or spoiler (can't quite remember which), that says you may have to try several times before the villager is successful, it would seem to be random. One thing I did notice was that if a runner was the one trying, on 1/2 speed "several" times became "endless" times. He would also only make one dive as opposed to two dives non-runners would make. I was growing totally frustrated, when I decided to try switching the speed up to normal, and bang, he got it on the next try. This has happened twice now.