If Luis's advice fixes the symptoms, you need to find the way to set up your server to support slasharguments. Unfortunately I don't know much about ngnix myself so redirecting to the docs is all I can do.
The setting $CFG->slasharguments will be removed in 3.0, even now some core functionality will not work with it disabled. So it is strongly recommended to fix the server configuration and not disable it. Feel free to start new topic with the more explanatory header, something like "Configuring Nginx to work with slasharguments", this way you will attract the knowledgeable people.