The given value of type String from the data source cannot be converted to type nvarchar of the specified target column

Process Data for a Collection fails with the following error message: 
 
The given value of type String from the data source cannot be converted to type nvarchar of the specified target column.  

Answer:
The error is probably caused by a varchar value that is truncated.
Try to increase the size of the nvarchar and run again. Use the Analyse Data Length functionality for the Collection you are working with to find the actual max sizes for varchar columns.