Hi Yacinus,
Thanks for posting us your query.
We can able to reproduce the issue as in attached image. If this is an issue, could you please try the below code snippet and Let us know.
//Maintains the GridGroupingControl's viewstate on PostBack
this.GridGroupingControl1.DataSourceCachingMode=DataSourceCachingMode.ViewState
GridGroupingControl_IssueIf this is not a case, could you please update us the steps to reproduce the issue and also please update us with the sample which causes this issue. It will help us to sort out the issue earlier.
Thanks for using Syncfusion product.
Regards,
Gokulkumar B