Issue with Tristate checkbox and Table Tree

Hello Experts,

I have implemented table tree in one of the custom apps I am developing. For selection, I have used Tristate checkbox. The issue is that when I select the Root node of table, the child checkbox state changes to selected( figured this out during debugging) but in visual they remain unselected. I have followed this example - JS Bin - Collaborative JavaScript Debugging.

I have also observed one thing that, this happens only for table type "Fixed". With type "Auto" it works but performance is real slow.

Any help would be appreciated.