Steps to Reproduce:
- Create a panel
- Inside the panel, place a file upload control
- Inside the panel, place a button of type "submit"
- Set the onlick event of the button to partial refresh with the ID of the panel
As a consequence, you cannot upload files anymore. The button saves the document, but does not attach the file anymore.
This is a third-party software bug. Dojo bug in dojo.io.iframe and dojo.request.iframe implementation - lots of posts on the issue that occurs under certain circumstances can be read on the web. The crux of the issue centers around the embedded iframe holding history on the last request that blocks subsequent responses from loading into the parent DOM when the embedded iframe is not within the target refresh area.