How to deal with files with %20 in name in Nginx
Think outside the box of web server configuration.

Install the Transliteration module:


  Provides one-way string transliteration (romanization) and cleans file
  names during upload by replacing unwanted characters.


And install the File Field Paths module:


  In simple terms, File (Field) Paths allows you to automatically sort
  and rename your uploaded files using token based replacement patterns
  to maintain a nice clean filesystem.
  
  Features ...
  
  Retroactive updates - rename and/or move previously uploaded files
  (Use with caution)


With both enabled you can goto the Content Type's Manage Field page and edit the field with the file(s) and enable Transliteration on the file name to be retroactively assigned to all uploaded files.

This will change the space character ' ' to '_' for all uploaded files.

Then you don't need to worry about difficult server configuration issues. I've used File Field Paths to rename thousands of files successfully on production systems.