CheckedListBox not show any items although they are added already

[manhnguyentien270489]

I using MaterialSkin 2 in my Winforms project (.Net 4.6). You can see in the bellow image
This problem also occurred with adding items programmatically

[nobrandnolabel]

Hey I got the same Problem.
You can add them via code with .Items.Add() but it's just a workaround.
Everything whould be much easier if there whould be working properties, also for events and the value handling of the items.