Advice needed- debugging corruption in Quicken file

Whether a download will include an 8 month old transaction is partly dependent on how long your financial institution makes transactions available for downloading. But I think it should be a moot point.

But once you download a transaction, Quicken should prevent that specific transaction from downloading again ... even if your financial institution still has the transaction available for download (assuming you are trying to download to the same Quicken account in the same Quicken file). Deleting the transaction from your Quicken account should have no bearing on this; once the transaction is downloaded - even if you don't "Accept" it, or you delete it after accepting it - it should never download again.

Since you are talking about one transaction, you should be able to use your printed statements (or get the appropriate statement(s) from Vanguard's web site) to determine whether that transaction was a legitimate Vanguard transaction, and if so, what its specifics were ... so you can enter it manually.

I think you should backup before taking any steps to "fix" the problem.

[And if the problem Quicken transaction has the security name you are using for a Fidelity security. it's possible you have mismatched securities. If so, you should uncheck the box "Matched with online security" for each of the two securities (in the Security List), and expect to link the downloaded securities to your Quicken securities the next time you download or do a Compare to Portfolio for the two accounts.]

Yes, that is one way; normally much derided (because of all those unwanted transactions) by those who are usually doing the deactivating/reactivating to try to regain communications with the financial institution. You can also achieve similar results by deleting the .QEL file from your Quicken fileset (though it's a bit more draconian than deactivating/reactivating) ... good for when you can't deactivate.

But it's significant overkill to try to recover one transaction.

If you just want to look at all the transactions available at the financial institution for download, you could create a temporary New Quicken file with just the one account and download to that file ... easy to get rid of those transactions. Or, I suppose, backup, deactivate/activate, download, peruse ... then restore the backup.