Can Someone ELI5 the Pa Mail Ballot Database Data Issues?

Thanks for clarifying. The ELI5 on this is somewhat simpler: there isn't one yet, because it's the next step of the process (by design). Well-formed ballots are counted immediately after the deadline, then the updated voter rolls are made available to candidates. As you saw, the voter rolls include everything except how the ballot voted. Candidates can then dispute/contest ballots they believe are well-formed but invalid. For close races, they inevitably do.

This generally occurs over a week or two after the initial certification, on roughly the same schedule as the recount. We've seen this a few times already for early results and will see it more in the next few days. https://www.dos.pa.gov/VotingElections/OtherServicesEvents/V... and https://www.dos.pa.gov/VotingElections/OtherServicesEvents/V... have a bit more on this, though there's probably another PDF I can't readily find which defines the timeline to dispute/contest certain ballots.

In practice this means that both parties' national organizations have teams running voters' names through public databases right now, looking for dispute-worthy ballots/voters. I've never been a part of a national race so I can't describe the details of that, but my guess is they use the same data brokers as debt collectors, plus some data brokers that are specific to voter rolls. l2political.com is the best known of the political databases (details: https://guides.nyu.edu/l2political).

So, the ELI5 is: it's the next step in the process between receiving ballots and final tabulation.

(Source: Have volunteered as a ballot-counting observer in Seattle, volunteered for a local City Council candidate's campaign, and am leading a campaign to change Seattle's voting method. I'm nowhere near an expert but do know a lot more about it than most people.)