Still working fine in my tests with resychronize enabled. That error is still unfamiliar. Do you have any 3rd party authentication plugins installed? Are you acting on profile update with CB Auto Actions or anything of the sort?

Switch your site to English so the string isn't translated or provide the language key for that translated string so I can track down exactly where it's coming from. I'm unable to confirm your issue across multiple sites.

The password is never even given to Joomla as it's an API login so that error shouldn't even be possible unless a Joomla authentication plugin or 3rd party Joomla system plugin is doing it (you need to review these carefully in Extensions > Plugins).

The english error string is saying: "Incorrect username or password. Please try again."

Ok, that's CBs. It's thrown when the user object can't be found during the login process. Somehow it's failing. Make the below adjust them then see if issue persists as maybe it's tied to the username resync.

IN: components/com_comprofiler/plugin/user/plug_cbconnect/component.cbconnect.php
ON: Line 391
FROM:TO:

Hmmm do I get blocked when I try to much ?? On another site I now get the error: "cURL error 6: Could not resolve host: graph.facebook.com"

They've rate limits, yes, but that'd be a different error message most likely. Depends entirely on how many times you're attempting within 24 hours. It takes quite a bit (thousands). You maybe being limited by your host on outbound CURL requests.