County election officials are running into an unexpected problem with the Department of Motor Vehicles’ new online voter registration system: faulty signatures. Without clear copies of voters’ signatures to compare to the poll books, the identity of New Yorkers who registered online might be challenged on election day, elections officials said. Digital scans of applicants’ signatures “are not as crisp as we are used to getting, and they could be blurry. They could be distorted,” said Louis Babcock, Rockland County Republican election commissioner. “It could be brought into question by a poll inspector,” he said. Uncertainty over a signature would not keep people from casting a vote, but it might require them to submit an affidavit ballot, which would allow commissioners time to obtain a better copy for verification, Babcock said.