Just to confirm, this is what happened - he paid one twice, and therefore the other became delinquent. However, if you file a FOIA request with the SFMTA and do some basic analysis on how much is "owed per license plate", you will see that certain license plates have been allowed to accrue tens of thousands of dollars in parking fines with virtually no towing repercussions, going back as far as data is available (2013). Around 80-90% of these vehicles are rental cars, around 5-8% of them are commercial trucking companies which absorb the cost of 2 tickets per day, and this tiny 1% of license plates are effectively "lawless parkers" who drive high-end cars and accrue tens of thousands of dollars in unpaid parking fines every year.