Commented Issue: CheckListBox SelectedItems not behaving correctly when having a pool of items [18709]

Please see the example, I think everything should be clear then: Select a bookshelf and add a book. EDIT: I found a workaround, see my second ZIP, maybe it helps finding the issue.
Comments: ** Comment from web user: mbulava **

I Still am seeing this issue.. I'm using a Flag Enum and converter but ConvertBack is never being called:

<xctk:CheckComboBox x:Name="_read"
ItemsSource="{Binding Path=Environments, Converter={StaticResource EnvironmentListConverter}}"
HorizontalAlignment="Center"
VerticalAlignment="Center"
SelectedItemsOverride="{Binding Path=Read, Converter={StaticResource EnvironmentListConverter}
, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged,NotifyOnTargetUpdated=True, NotifyOnSourceUpdated=True}"
ItemSelectionChanged="_combo_ItemSelectionChanged"
/>

Both the ItemsSource And SelectedItemsOverride are being set to Observable Collection but I can't get the changes to the combo to update the underlying property