Based on the screenshots you have provided, we can only guess how your table is setup exactly, so in order to provide an accurate reply we would need a sample report.
Generally the correct way to handle such case is to set the GroupKeepTogether property of the respective group to True. However in case you only have a detail group, it would not have a report item by default and this is currently required for this functionality to work. What you can do is add a parent group to your table (it would contain a report item), delete the grouping criteria and alter the GroupKeepTogether to True.
If still having problems, please open a support ticket and attach a sample report that we can look into.
All the best,
the Telerik team
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