Admin System bringts an Internal Server Error

After clicking on Admin / System (left bottom) there appears:

Internal Server Error
The server was unable to complete your request.
If this happens again, please send the technical details below to the server administrator.
More details can be found in the server log.

Plesk Logfile
Error 500 GET /index.php/settings/admin/serverinfo HTTP/1.1

Have anyone an idea, how i can solve thatß

duplicate, closing this in favor of Admin / System - no