Our hunch is that the problem is caused by the user using a subaddress, like firstname.lastname@example.org. Given instructions, we can produce a HAR file if that would help, e.g. if someone at Auth0 who creates a Facebook account with a plus-address email, can’t reproduce the issue.
Hey there @Civility, if possible could you please share with us steps to reproduce this along with a recent HAR file capture of the of the login workflow through direct message? Please be sure to select “Preserve log” to catch redirects and scrub the file of user passwords before passing, thanks!