Weired redirect url after trying to login as non superadmin to one of my multisites

Hey guys,

every time i try to login to one of my multisites (except the #1 page) as a non-superadmin (as an Editor in my case) i get the following redirect url:

Iam running Wordpress 4.2.1 and Domain Mapping

My htaccess, wp-config and domain mapping settings are nothing unusual and everything worked just fine before the Wordpress 4.2 update.

I have no domain mapped at the moment, but the plugin installed and activated. If i switch it off, the problem is gone. Also switching off every other plugin did not solve the problem.