This help article lists common issues on binding data to Telerik Reports and nested data items. Before proceeding with the troubleshooting, test if the problem is reproducible with the latest available Telerik Reporting version.
Data can be visualized by data items. Each data item has its own DataSource property and creates a separate Expression scope. If both a report and its nested data item are bound to the same data source, each will develop its designed template per data record in the data source. In such case, you need to check which data item will visualize the data, and to reset the DataSource property of the other item.
Data can be visualized by data items. Each data item has its own DataSource property and creates a separate Expression scope. To change data at run-time, you need to iterate all data items and to modify their DataSource properties e.g. Changing the connection string dynamically according to runtime data. You can also use the ReportItemBase.ItemCollection.Find Method to get the data item visualizing data, and to change its DataSource property's value.