Well, neither of those cases involved any of Project Vote's field partners. Project Vote itself implements the most comprehensive quality control and anti-fraud procedures of any VR group anywhere. Every card is called back to verify data and there are numerous steps that must be followed, each of which creates a trail that can be traced back to a specific VR worker. We also do data matching and voter verification to see if folks are actually getting on the rolls.
However, any large-scale VR drive will have cards that slip through the cracks. Humans are fallible and the system itself is set-up to narrow the electorate, not expand it. There are numerous stages at which a card can fail, despite one's best efforts. This does not indicate an attempt to rig elections so much as an attempt to get paid for not doing the work.
One thing to remember is that no case of voter registration fraud has ever been linked with a case of electoral fraud (say an illegally cast ballot, for example). Accusations of voter fraud related to bad cards, though, are often used to drum up support for disenfranchising laws like voter ID, proof of citizenship, and draconian regulations of voter registration drives.