User account will get very slow.....
When changing a calendar event to a repetitive event, you select the interval (day, week, ...) but do not fill in the number of (days, weeks, months or years) the user account gets very slow. It takes about 15minutes to be able to select something. The calender will not show.
Logout and login will not help. After login you will have to wait about 15 minutes again.
When you wait long enough you can go to the repository and correct the calender event. You will see zero as number repetition increment, when you change it to at least 1 or change the calender-event to normal, the system wil react normal again...