Ambiguities in the intended language aren't literally "still there" in the PEG, but realistically they are "still there" as a source of problems: naive PEGs can

Ambiguities in the intended language aren't literally "still there" in the PEG, but realistically they are "still there" as a source of problems: naive PEGs can remove ambiguities incorrectly in less than obvious ways, and figuring out what's wrong can be more difficult than hitting a brick wall with other parsing approaches.