Got this error while trying to import a managed solution in CRM 2016 Online.
During analysis we figured out that it was pointing to one of the charts created for System User Entity. It seemed like chart’s xml was modified after export and then imported. The xml definition of the chart contained distinct keyword.
Removing the distinct keyword from the Chart definition and importing it back and then importing the managed solution with this updated chart got imported without any error.
Hope it helps..