Problem report from an 11-year Dropbox user - currently at the Dropbpox Basic level (as my company has a Dropbox Advanced plan).
I typically login to Dropbox Basic using latest Chrome version on Windows. My account normally has two-step verification Disabled. But yet I am often required to enter an emailed code anyway to complete the login.
For months now, this happens whenever all Dropbox related cookies have been erased in the Chrome browser. (Easy to re-create using Incognito / InPrivate windows.)
This typically does not happen when I just sign out via the Dropbox menu. Then the next time I login, there is no two-step verification, in accordance with my settings.