Editable Grid Tree - Unable to add a selection

Hi, 

I am following https://docs.appian.com/suite/help/24.2/recipe-expand-collapse-rows-in-a-tree-grid.html to create a Proof of concept. I have dropped collapsible functionality as my intent is I should have a header and sub items below it as shown in this recipe. I have done that successfully but when I try to add the selection check box , there is a problem , 

as this grid is written using loop within loop, when I try to select an item in first section, the item in second section also gets selected. Please let me know if there is an alternate way to resolve this. 

Any help is appreciated.