Reordering new item on Repeater relationship throw error

Repeater::make('shifts')
    ->relationship('shifts')
    ->orderColumn('sort')
    ->reorderable(true)
    ->schema([
        TimePicker::make('start_time')
            ->required()
            ->native(false)
            ->seconds(false)
            ->minutesStep(30)
            ->live('onBlur')
            ->afterStateUpdated(function (Get $get, Set $set) {
                $duration = $get('../../duration') ?? 0;
                $time=Carbon::createFromFormat('Y-m-d H:i:s', $get('start_time'))->addMinute($duration);
                $set('end_time', $time);
            }),
        TimePicker::make('end_time')
            ->required()
            ->native(false)
            ->seconds(false)
            ->minutesStep(30)
            ->rule('after:start_time'),
        ])
    ->addAction(function (FormAction $action) {
        return $action
            ->label('Add Shift')
            ->action(function (Get $get, Set $set) {
                $shifts = $get('shifts') ?? [];
                if(count($shifts) > 0) {
                    $last = end($shifts);
                    $duration = $get('duration') ?? 0;
                    ($last) ? $start = $last['end_time'] : $start = null;
                    $shifts[] = [
                        'start_time' => $start,
                        'end_time' => Carbon::createFromFormat('Y-m-d H:i:s', $last['end_time'])->addMinute($duration),
                    ];
                    $set('shifts', $shifts);
                } else {
                    $shifts[] = [
                        'start_time' => null,
                        'end_time' => null,
                    ];
                    $set('shifts', $shifts);
                }
            });
    }),