My report on duplicate (and other) ID issues is finished. I have it available as both a
Google Sheet (just the problems and fixes) as well as an
Excel File (includes the full database this was build off of, though all non-problems are filtered out). The Player ID numbers come from a roster.tar file provided by Lucas Berger which included a CSV of the (hopefully) full 54855-player database. Conditional formatting is set to flag in red both players with an ID issue in the current ID column, as well as players who do not have a simple fix in the fix column. This covers potential same player issues, as well as a few odds and ends like the "draft" and "contest" minors IDs.
Unfortunately, I cannot call this a comprehensive list of errors, as like I said earlier, my methods will only check procedurally incorrect IDs. Anything that was a unique 12 character ID with no illegal characters was flagged as okay, which means there are undoubtedly some errors still hanging around. However, I would hazard a guess that this covers the majority of issues.