iCloud Drive - stuck uploading one file
I have iCloud drive enabled - with many GB of data.
For many days now the sync indicator has looked like this:
And if I click on the progress indicator I get this:
And it has been stuck on "Uploading 1 item" for about 5 days now.
I have no idea how to find out which file is being uploaded because none of the folders or files in my iCloud drive have the "cloud" symbol on them which normally indicates syncing activity.
The problem persists after a re-boot.
How can I check which file is stuck? Are there any iCloud diagnostics available?
iMac, OS X 10.11