dhtmlx tree grid loading large data issue

I am trying to load heirarchy data in my dhtmlx tree grid.
For small data sets, tree grid loads properly and the sum of values in the heirarchy is rolled up properly.

Issue occurs with large dataset typcally greater than 1000 entities, Grid breaks down and displays NaN as values for summations.
When Sum functionality is removed data is loaded properly in the grid.

Has someone encountered such an issue and can please suggest what a work around for this.