I have investigated this problem further. Here's what I've found:
In Quicken Classic Deluxe Version R54.16, Build 27.1.54.16, the most current version for Windows 10, “One Step Update” is failing to download charge transactions from a Chase VISA credit card in the following scenario:
If there are two transactions from the same payee posted on the same date with different amounts, only one will be downloaded into Quicken.
However, the .QFX file downloaded from the Chase site shows both transactions with the exact same payee <NAME> (as it should), the exact same date posted <DTPOSTED> (as it should), with clearly different transaction amounts <TRNAMT> (as it should), and different transaction identifiers <FITID> (as it should),
USER WARNING: As expected, if you attempt to reconcile this account, all other things being equal, the reconciliation will differ by the amount of the transaction that did not download.
Please DO NOT attempt to correct this by using “Tools/Account List/Edit/Online Services/Reset Account”. When I’ve done this, here is what happens (no, I’m serious!):
The final register balance in Quicken’s register for the account WILL BE CHANGED to equal the chase online balance, even though the transaction will still be missing.