I have some blogs, and after upgrading to 5.1.1 I always have to reauth myself. If password/username is wrong, I got that error message but if I enter right data, the page simply reloads. So I go to:

it then redirects to:

.php?redirect_to=https%3A%2F%2Fwww.example%2Fwp-admin%2F&reauth=1

and even I enter the right account data, it just reloads the site.

Of course, clearing all browser data helps - but next day, this bug occurs again. I dont think its a good solution to clear my browser everytime when it happens.

EDIT: Its Php 7.3 and nginix

EDIT2: I added this line to my config:

define('FORCE_SSL_ADMIN', false);

so far works well. I dont know what it is by the way.