Zimbra not saving attachments added to shared calendars

So I just tried creating a calendar entry and inserting a screen-shot image.
Once closing out of two shared calendars and returning, both
images had gone...and with this I received the attached emails which clearly
correlate to what just happened. I never noticed before that these error
reports were related to the calendar action. Error log attached.

Is this something we can resolve before I go down the re-syncing route?

Many thanks,

Iain