Trying to push a may to ArcGIS Online using ArcGIS Pro. Each time I process the share to online it shows duplicated values. I am publishing it as a Hosted Tile Service as I have customized symbology. I tried exporting as its own layer rather than a map and it happens again.
Below are my settings currently being used for labeling of this Layer and Class.
I would have to assume based on your label settings that there are either two layers in the map, or there are two "Washington" features.
Can you confirm whether or not there are multiple features in that spot, and that there's just a single layer in your Contents pane?
Worth pointing out: vector tiles allow patterns for fills and lines.
We don't use image tiles much here, but when I generate a test tile pack from your layers, I get the same issue! If fact, as I zoom in, I see more than two, and for the other features, as well:
I'd guess there's a "cutline" between tiles, maybe, and that it renders labels for each tile independently?
What you might do to address this is to set the label position to being "fixed". This will keep your labels centered in the feature regardless of scale.
Here are two maps: left is the original tile pack. Right, tiles generated with the "fixed" setting.
Thanks for the data - so I tested this a few ways. Shared as a Web Map with default settings (some symbology) would be degraded and viewed the Web Map in the Classic Map Viewer and the Beta Map Viewer. No duplicate label for Washington. I shared it as a Feature Layer with default settings and added to a Web Map in ArcGIS Online. No duplicate label for Washington. Lastly, I shared it as Tile Layer with default settings and added to a Web Map in ArcGIS Online. Duplicate label for Washington. So clearly something is up with sharing as a Tile Layer. I'll keep digging.
There is BUG-000116520 Vector tiles are repeating labels in linear features in ArcGIS Online (and Portal). It seems to be with polygons too! Are you using Maplex as well? Try the Standard Label engine and repeat your workflow.