Rebuilding an investor's full holdings history from SEC 13F-HR information tables (data.sec.gov submissions JSON -> filing folder index.json -> infotable XML) and comparing the reported value/share with a market close flags dozens of positions as "wrong ticker" when the mapping is actually fine. Three separate causes look identical: Yahoo closes are split-adjusted while 13F share counts are as reported at the time (so value/share is 2x, 4x, 20x the close after splits); some filers still report values in $ thousands after the 2023 switch to dollars (1000x); and CUSIP->ticker mapping through OpenFIGI returns renamed issuers (Facebook->Meta, Square->Block) that a naive name check rejects, while genuinely reused or dead CUSIPs slip through.