I am testing the same thing with a user that has a maxed out iCloud storage. The debug log clearly states that the error is related to quotaExceeeded but the eventChangedNotification received only mentions a partialFailure without any CKPartialErrorsByItemIDKey so there doesn't seem to be a way to come to the conclusion that the issue is with the storage quota being exceeded just by listening those notifications, is there? Does it matter if it related to a shared db?

Thanks for sharing. When I read through that sample code after WWDC I though it had good bit about testing, etc, but at the same time it felt a bit outdated. The link I had mentioned to the more recent demo also talks about empty notifications for shares in a comment. Until I saw that, that was causing me grief too

Thanks for the tip. I am using Safari. In the end I got around the issue by first establishing a VPN connection to a different country and then starting a fresh download. I guess my IP was being sent to some cache engine or a server hosting a corrupt file