This is because of a limit of elastic search (see Tony’s explanation above).
The “fix” is also the same as described above – use search parameters to get to what you want. You can use the API (info here), and pisum has already made a friendly tool for it here. If you’re just looking for your oldest ID, you can use https://jumear.github.io/stirfry/iNatAPIv1_identifications.html?user_login=joe_fish&order=asc.
You can also vote for the feature request to add better searching for IDs.