Paging issues on Grid loadXML firing 2 calls to servlet


I have a tree grid in a tabbar which implements the kidsxml approach to load the child nodes dynamically.
However when the user clicks on the + icon and data is absolute leaf nodes then it appears in a new tab in a paginated grid.

So what I have done is that I have attached an event onOpenStart and if the call is for leaf nodes I load the paginated grid in a new tab.
What I see however is that the pagination is quite not working in this grid. And I see 2 calls made to the server side for data one is for first 50 records(size defined by me) and other call for rest of the records.

I can’t understand why the call is being made twice in this case.
I find following part in dhtmlx.js after which another call will be made.

I see that render_data() method is being called twice once for initial data and other for rest of the data.

Can anybody help?