Change UITableView row section at runtime

I have a UITableView that is controlled by NSFetchedResultsController. Lines are organized in sections from a row property. But when I change this property, the application ends:

Invalid update: invalid number of sections.

Each line is a picture in the film, a wide shot, a close-up, etc. The row also contains the scene to which it belongs, and sections are computed from this.

Shot.m (CoreData object)

#pragma mark Transient properties

- (NSString *)sectionIdentifier 
{
    return [self sceneNumber];
}

ShotsViewController.m (UITableView)

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
    id <NSFetchedResultsSectionInfo> theSection = [[self.fetchedResultsController sections] objectAtIndex:section];
    return [theSection name];
}

I don’t know what I should do here. I played with UITableView insertSections and deleteSections, but always get the same invalid number of errors in sections.

Edit

it automatically moves to other existing sections:

- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
           atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {

    switch(type) {
        case NSFetchedResultsChangeInsert:
            [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeUpdate:
            [self.tableView reloadSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}

It worked after I added

case NSFetchedResultsChangeUpdate:
                [self.tableView reloadSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];

But now, let's say, I have two cells. Cell1.sceneNumber = 1 Cell2.sceneNumber = 2

Cell1.sceneNumber = 3, :

Invalid update: invalid number of sections.  The number of sections contained in the table view after the update (3) must be equal to the number of sections contained in the table view before the update (2)