A large number of transactions in my register show the same payee (a local restaurant).

Look at your renaming rules. most likely you have one for that restaurant name that is to "general" and is match a lot of your downloaded payees and changing them to the restaurant name.

Tools -> Renaming Rules

You might also want to look to make sure that Quicken confirms any creation of renaming rules:

Edit -> Preferences -> Downloaded transactions -> Let me review/confirm the automatically created rules

Also in the register you can turn on the Downloaded Payee name to help you correct those transactions the second gear icon on the right of the register.

Another thing you can do is right click on a transaction and there is both a review and a revert menu item changing back to the downloaded payee.