Upload file widget issues

Using the upload form widget for users to submit word document or scan document to Reporting form, one user upload a word document, but I am not able to download his word document, received an error message, see screenshot. He tried 2nd time to upload, but same error msg.

Other users do not have this problem.

And idea what cause this problem?

Thanks. 

Could you please let us know on which form you're experiencing this problem so we can investigate further?

Or, possibly, the file URL that you're trying to access.

We'll wait for your response.

Thank you!