Every user have to login twice since NC 12.0.0


we use our AD for authentication on our NC 12.0.0 server. Since the update to NC 12.0.0 every user have to login twice. If I type in username and password the screen will be reloaded and I have to do it again. Then the login is working. This also happening with local NC users.
The first login I cannot see in the NC log, the second logging I can see.
Also the dashboard is not very stable. If I change from files to Activity it can happen that I fall back to the login screen. If I login than I’m in the Activity. Very often the users receive the message:

Does anyone have an idea what I can check?

What have I done until now:

  • Tested with local our AD users
  • Checked my firewall setting that NC have access to AD
  • Checked the settings in the php.ini
  • Checked with different browsers

Nextcloud version 12.0.0
Operating system and version CentOS 6.9
Apache 2.2.15
PHP version 5.6.30