Error 4xx while downloading a file through API which has second word's intials H for eg. (DX Haley)

I can't reproduce this error. Here's what happens when I try it:

$ http get "https://api.dropbox.com/1/metadata/auto/Test test.txt" 'Authorization:Bearer <REDACTED>'
HTTP/1.1 200 OK
...
{"read_only": false, "revision": 47485, "bytes": 4, "thumb_exists": false, "rev": "b97d10f8d89e", "modified": "Thu, 02 Apr 2015 15:43:00 +0000", "mime_type": "text/plain", "size": "4 bytes", "path": "/Test test.txt", "is_dir": false, "modifier": null, "root": "dropbox", "client_mtime": "Thu, 02 Apr 2015 15:43:00 +0000", "icon": "page_white_text"}

$ http get "https://api.dropbox.com/1/metadata/auto/Test hest.txt" 'Authorization:Bearer <REDACTED>'
HTTP/1.1 200 OK
...
{"read_only": false, "revision": 47486, "bytes": 4, "thumb_exists": false, "rev": "b97e10f8d89e", "modified": "Thu, 02 Apr 2015 15:43:03 +0000", "mime_type": "text/plain", "size": "4 bytes", "path": "/Test hest.txt", "is_dir": false, "modifier": null, "root": "dropbox", "client_mtime": "Thu, 02 Apr 2015 15:43:03 +0000", "icon": "page_white_text"}

Could you share some more information?

1. What programming language are you using?
2. Are you using an OAuth or Dropbox library? If so, which one?
3. What does GetProperties.getDropBoxMedURI() return?
4. What's the exact value of fileName (both in the successful and unsuccessful calls)?
5. What is the code for OAuthBearerClientRequest, including its buildQueryMessage method? (Perhaps that's from a library?)