Even though this is not inherent to DropzoneJS, but rather to Drupal core Javascript + Chrome, I experienced it heavily when using FileBrowser + DropzoneJS. The problem Validation error is triggered when double-clicking on "Select entities", the message displayed is: "At least one valid file should be uploaded.". This is the case for the Chrome web-browser, Firefox seems to be fine. Reproducing You can easily reproduce this problem without killing your index-finger. Fire-up your Chrome Simply add a sleep(2) at the beginning of the DropzoneJsEbWidget::validate() function.

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The File (Field) Paths module extends the default functionality of Drupal's core File module, Image module and many other File upload modules, by adding the ability to use entity based tokens in destination paths and file names. 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: Configurable file paths now use entity tokens in addition to user tokens. Configurable file names. Support for file based fields, including but not limited to:   Drupal core File module  Drupal core Image module  Video module.   File path and filename cleanup options:   Remove slashes from tokens.  Filter out words and punctuation by taking advantage of the Pathauto module.  Convert unicode characters into US-ASCII with the Transliteration module.   [D7] Automatically updates unprocessed file paths in any Text fields on the entity. Retroactive updates - rename and/or move previously uploaded files. Active…