Hi Dali, I can’t reproduce this bug, but I remember there being a similar bug in the past. With the old bug there was an error that occurred which (for some reason) resulted in an empty datatable being displayed instead of the error. Can you check your webserver error logs (or piwik logs) for any clues? If there’s nothing there, would you mind sending me a private message with the hierarchical data that won’t be flattened?
there is another bug after bugfix in /path/to/piwik/core/API/DataTableManipulator.php.
Go to demo.piwik.org , select 2013-07-01 and the Actions > Page-Report, make it flat,
so there are lots of page URLs without Bounce Rate, without Exit Rate but with Avg. time on page = 0s. The correct values are displayed in the hierachical view.