This article provides a solution for how to add section keys manually to a report. You might see this warning after trying to run "Fix report":

This report section keys are not possible to fix automatically. You must add unique keys in sections manually by using Visual Studio.

Resolution

To remove the validation warnings, the placeholder LACRecId_DONOT_CHANGE must be added manually to fields in the report. 

Additional information

Lasernet plugin does not support automatic fixing for reports that are based on Query rather than on DataSource class.