SelectionId from data received with fetchMoreData()

I have a problem with the fetchMoreData() function.

I'm able to retrieve all the data from my dataset, but when I try to generate the selectionIds, something strange happens.

I use this code to generate the selectionIds:

host.createSelectionIdBuilder().withCategory(category, i).createSelectionId();

After receiving all data (in the last update), I create an internal data model and assign selectionIds to each data point. The data points in the first segment (let's say the first 500) have working selectionIds, all the others have something like this:

Am I doing something wrong?

Thanks