SharePoint Document Viewer - intermittent 404 issues

Hi Team

We are experiencing intermittent 404 File Not Found issues when we search documents from our search engine. These are for our controlled documents (eg policies). You either need to refresh the page or close the page and re-open it to finally open the document.

There seem to be no pattern as to when the 404 error would appear. Is there anything we can do to avoid this? Don't want our people to think system is broken.

Cheers!