Another unusual circumstance is when you're the first users who have just installed the latest software update, a fingerprint testing website will identify you

Another unusual circumstance is when you're the first users who have just installed the latest software update, a fingerprint testing website will identify you as an unique user. But you won't be unique anymore within a few days. It happens a lot in the Tor mailing list. Often, a new major release of Tor Browser comes out, a user is shocked by the upgrade, "OMG! I'm unique and trackable!". Don't panic, just keep using it.