The online audio assignment type returns a blank/white screen after file upload, if portfolios are enabled on the site (enableportfolios setting).
For the steps below, it's easier if you have two tabs or windows open, so that you can easily flip from the site settings to the course page.
1) Ensure that the enableportfolios setting is ENABLED on your site.
2) Add an Online audio recording assignment to a course.
3) Ensure you are a participant in the course, or you will not see the Add Submission button.
4) View the assignment and click on Add submission.
5) record a short audio clip, save and upload.
At this point, the page goes blank.
6) Use the back button of your browser to return to the course page and refresh the page.
7) Try to return to the assignment page by clicking on the assignment link on the main page.
The page will be blank, again.
8) Use the back button of your browser to return to the course page and refresh the page.
9) DISABLE the portfolios.
10) Attempt step #7, again. It will now work.
11) Return to the course main page.
12) ENABLE the portfolios.
13) Attempt step #7, again. It will return a blank/white page, again.