Events I add to korganizer don't get uploaded to google calender and korganizer requires manually syncing from akonadiconsole to get events added on google calender to appear in korganizer. Essentially it is pretty well borked - this has been going on for <ages> and it doesn't take that many missed appointments to render korganizer history.
please try a more modern version 5.2.3 is pretty old by now.
I can confirm that upgrading to v5.5.3 has fixed this problem - thanks