(2006) have identified a number of problems with BLEU and related n-gram-based scores: (1) BLEUlike metrics are unreliable at the level of individual sentences due to data sparsity; (2) BLEU metrics can be "gamed" by permuting word order; (3) for some corpora and languages, the correlation to human ratings is very low even at the system level; (4) scores are biased towards statistical MT; (5) the quality gap between MT and human translations is not reflected in equally large BLEU differences.
together with the subject mismatch, MtR correctly predicts a low score (rank 5/5).