MapViewer Legend displaying repeated symbology

[ahargreaves_FW]

Hello

I have data in Pro, symbolized via attributes (see 'Pro Symbology' screenshot). This gets published as a Feature Service to Portal 10.9.1. The Features Services 'Visualization' tab shows the symbology as the same (see 'Layer Visualization' screenshot). However, when I bring this feature service into a map the MapViewer legend display repeated symbols (see 'MapViewer Legend' screenshot). Anyone any idea why?

Thanks

Pro SymbologyLayer VisualizationMapViewer Legend