Trying to change the categories for a google calendar event produces an error from google calendar "Conflict" is the error.
If you take a none-categorised event and set an event to it, it works fine. But if you again change the category on this event to something else, the error is produced, and continues to be produced for every sequent attempt to change the category. Also when updating rainlendar, the correct category will NOT be shown anymore. After updating the calendar, another category change is allowed but any subsequent ones after that produces the same problem.
Also, from time to time I get an error downloading my calendar even though there is no problem with google or my connection. Hitting "update" always fixes the problem. Maybe an option should be added like "if update failed, try again after 10 seconds before giving up".