https://www.sos.texas.gov/elections/laws/jan2019_dominion.shtml

This poor resolution on the scanner also failed to pick up some of the printed wording on the ballots. In a follow-up, the vendor stated that only black Sharpie markers should be used for marking the ballots; however, when the black sharpie was used during testing, it did, on a few occasions, bleed through to the back side of the two-sided ballot in such a way that it could confuse the ballot scanner or kick the ballot out.