Scroll in the huge listbox is loosing the selected check boxes.

Steps to reproduce

1) Select 1st Listitem
2) scroll down to last listitem
3) select last or items near to it.
4) Scroll up to first selected listitem and we see its now unchecked.

Current result

the 1st item is not selected

Expected result

the 1st item is selected

Debug Info

• I have attached the sample code taken form zk sandbox to recreate this issue
• this bug also happen when using a model