I too am having issues with saving. For me, this error has occurred when creating an Illustrator document on the Mac containing a jpeg image on a layer for tracing and then opening the cloud document on the iPad. Subsequent work on the iPad will not reliably save. To be clear, this is not an issue of slight latency in the display of updates or a minor sync error. An hour of work on the iPad can easily be lost. -- Unrecoverable on the iPad or desktop.