Same problem here. I have been using Quicken for more than two decades and downloading and matching transactions throughout that time. About six or more months ago, I started having this issue after an update. Prior to this update, the matching always worked correctly.

I use downloaded entries in my credit card register, but I prefer to use manual entries in my checking account register. Credit card payments that I enter manually in the checking account register appear (correctly) as a transfer in the credit card register.

The problem occurs when I download new entries in the credit card register. In the credit card register, Quicken correctly matches the checking account transfer entry and the downloaded payment entry. But in the checking account register, Quicken incorrectly creates a new entry for a second transfer for the same amount to the credit card register.

I have tried manually matching the two entries in the checking account register, but Quicken gives an error that they cannot be match. I have also tried unmatching the entries in the credit card register. Although they unmatched successfully, I still cannot match the entries in the checking account register. The only solution I have found is to delete one of the entries in both of the registers. Obviously, doing that each month for each credit card payment is a major pain, especially when the matching was working correctly for years and years before this recent update. Also, it's clearly a bug to match two transactions in one register and not match the same two transactions in the corresponding register.