At least 600 Californians, including lifelong Republicans and Democrats, have had their voter registration unexpectedly changed, and several county elections officials are pinning much of the blame on the state’s Department of Motor Vehicles...Usually I try to live by the maxim "don't attribute to malice what can more easily be explained by incompetence", but in California, you can never be too sure. In this case it's probably "and", not "or".
Elections officials across the state are linking many of the reported complaints to the state’s new Motor Voter program, which launched ahead of the 2018 midterms to automatically register eligible voters when they visit the DMV. The 2015 law was designed to help boost participation, but a rushed launch prompted 105,000 registration errors to occur following its roll-out.
Update, 12/15/19: I checked my voter registration online and my party affiliation hasn't changed.