Why do maps added to the Portal for ArcGIS map viewer display labels in the legend as 'Override X' when using a print service?

Answer

This is a known limitation of print services (as of version 10.5). When adding a hosted feature service to the Portal for ArcGIS map viewer, printing a map with a legend causes labels in the legend to be displayed as 'Override X' instead of the correct label names.

This behavior is due to how the map viewer creates range values for labels in the legend. The map viewer uses a dynamic JavaScript method that allows label values to change as more values are added to the map. When printing a map with a legend as an image or PDF, the print service does not fit each label patch in the legend according to the template's specified area, and therefore overwrites each range label with 'Override X'.

This behavior also occurs if the symbology is changed in the map viewer or when transparency is set. When the layer does not have the default symbology, the print service considers the symbol change (or transparency) an override, and sets the legend labels to 'Override X'. As a workaround, use ArcMap or ArcGIS Pro to set the desired symbology before publishing and printing the map.

Note:
This issue may also occur when printing via the Print widget in Web AppBuilder for ArcGIS applications, or when printing in the Basic Viewer application template.