Hi, 
i don't understand why this problem only appears when im trying to edit the root page (home). 
All subpages are working. 
I made a video of the problem: Video 
My boss made an update yesterday from php version 5.3.29 to 5.6.17-1~he.2 (At the moment i am not able to downgrade the version) 
Maybe this is the reason? 
My Processwire Version: 2.7.2 
MySQL-Version (PHPMYADMIN) 
 
MySQL-Version (phpinfo();)