Jira Api doesn't return correct file from issue attachment

[John Smith]

Hello everybody

I have task with docx attachment. The attachment contains japanese name and content.
For download file I use link like this https://host.atlassian.net/secure/attachment/10019/【部門向け】インターシップ説明会資料_.docx.
But after downloading I've got .txt file instead .docx with content 'errormessages.' 

Could you explain how it happaned and how to fix it?

Best Regards.

[John Smith]

Jira api return 403 error.