Why does the final example in figure 14 fail completely? The outputs are correct as far as they go, but they're all incomplete. Is it because the scoring metri

Why does the final example in figure 14 fail completely? The outputs are correct as far as they go, but they're all incomplete. Is it because the scoring metric has a point where enough of a good start outscores an alternative in the beam search that could lead to a more complete solution? In non-trivial real-world examples, would the be a major problem?