Quicken Classic Premier for Windows R57.26 incorrectly, insanely duplicates transactions in an account register. It duplicates downloaded transactions. It duplicates hand-entered transactions, too. If I delete a duplicate transaction, then the original transaction is also deleted, or it is mangled. If I edit a mangled transaction to correct it, then another duplicate is created. Quicken is completely unusable. Quicken Support's only suggestion was that I update Quicken to the latest version. I did so and, if anything, the problem got worse. Possibly relatedly (Idunno), yesterday Quicken could not be started from my Windows 10 Desktop. However, restarting Windows solved that problem.