Objective-c - iOS system calendar insertion event fails

Question

I want to insert an event in the system calendar, the code used is as follows:

    NSError *error = nil;
    if (NO == [store saveEvent:event
                          span:EKSpanThisEvent
                        commit:YES
                         error:&error]
        ||
        error) {
        IMOAssert(false);
    }

The return value of each call is YES. But the final result is that in the system schedule, you can see the event I inserted. After 1 or 2 seconds, the event disappears automatically. Sometimes events will not disappear automatically, but if 2 or 3 events are inserted in the same time period, the event inserted first will also disappear, or even all events will not be displayed, and the set reminder will also become invalid.

Has anyone encountered similar problems? Any good suggestions? Thanks!