It was very finnicky for me as well. In the rest of the game, something vaguely resembling a straight line, of any length, can be registered as a cut. For some reason they require great precision in that one spot (and there are a few others later in the game that get finnicky like that too). Just keep plugging away with large slashes. I think they like the body of the scarecrow to be cut diagonally, but i could be wrong (i played that game way back in May)
Monster Hunter: pissing me off since 2010.