Although the issue I am writing about doesn’t exist anymore in version 13.x, it is still relevant to lower versions.
Namely when a user fails to change their password before their password expires completely they can’t log in to the web interface any more. They don’t get an error saying that their password is expired. Neither do they get a prompt to change it. They actually get an error about invalid credentials.
Initially when investigating the issue, I changed the affected users passwords manually. But then I asked one user to try and log in using SSH. What happened was, he was prompted to change his password. After that, he could successfully log in to the web interface again. And no that user did not have CLI permissions. So if you are not in a hurry to upgrade to versions 13.x and up, you still have a workaround.