convertView object is non-null for every entry except first in getView() method in Android 6.0

I am using BaseAdapter to display customized view of list. It contains text and checkbox. I found 2 different observations in Android 5.0 and 6.0. List entries are too small in count that it does not need scrolling in the view.
Android 5.0 --> convertView object in getView() method is everytime null - as expected and working fine.
Android 6.0 --> convertView object in getView() method is everytime non-null except 1st, that is without scroll. Is there any more thing need to handle in new Android 6.0. I am handling checkbox.onChangeListner(...) in the view. Since everytime I am getting older holder object and when I am setting checkbox value, it triggers checkbox.onChangeListner(...) event.

Has any encountered this kind of problem? Need Help.!!!