Hi Lucas ,
Greetings from Syncfusion support.
We suggest you to follow the below steps to resolve this issue. In your code, you already have the id for the rows you have selected, by using that id’s you should find out the row indexes. By giving the row indexes into the selectRows method leads to the selection of particular rows. This will done while paging operation. The whole operation is proceed under DataBound event because this event will trigger for each paging of the grid. Documentation links are given below for your reference.
Note: Once you have click for paging then dataBound event triggers and in that event you can select rows using SelectRows method.
Documentation Links :
Please get back to us if you need further assistance
Regards,
Thavasianand S.