I have 7 web apps and 7 different web maps (one for each app). All of a sudden, yesterday, one of the web maps started to not honour the symbology that was set in the web map. It was only with the polygon layers. The web app has started filling in 3 of the polygons feature services when all of the settings, including in the visualization settings of each feature service, has the polygons shown only with a black outline - no fill. I have deleted the map, recreated an entirely new map. Deleted the app and recreated an entirely new app. I have changed the basemap. I have removed the feature layers from the map then added them again... I still get the same error from the web application - where 3 polygon layers are shown filled in and not as just outlines.
EDIT: Now it is doing this for all polygons within my map and for all maps, but only in the web app builder, not in the map itself. I hope someone has some advice out there!!?