Ballot stuffing by the Dems for sure. There was no way she could swing over 17000 votes with less than 80,000 ballots.
This is bullshit, of course, but I doubt you care. It was 120,000 ballots, and the swing was only about half what you are suggesting. IIRC the last thing I had seen was that McSally's lead was less than 10,000 before the next batch was included in the totals. The ballots were from heavily Sinema friendly precincts. It's not surprising that she took a thin lead. There are still many absentee ballots to be counted, and many of those are expected to be military voters that are expected to favor McSally.