It cleared up for us, but we were also dropped the original feature service and rebuilt it from the ground up. Not a pleasant experience, but it let us get the issue resolved.
Sorry to see that you're still having an issue. Is this the site where you're having issues https://open-data-stancounty-gis.hub.arcgis.com/ ?
I have reproduced the issue and I've marked a fix has high priority. In the meantime, I suggest that you try making those items private and then public again. Afterward you may need to remove the link and re-add them within the gallery cards.
The problem comes from the fact that these those gallery cards link out to items referencing services that have multiple layers. The update is still tying to reference the original URL without knowledge that this is a layer. For example, if you click the Annexations gallery card link, you'll route to https://open-data-stancounty-gis.hub.arcgis.com/datasets/d32e342982c849839aa787a1ae513f15_8/explore?...
instead users should be route to a slightly different URL
We recognize that these bugs are very impactful and that the routing is confusing. Near-term we are adding additional tests to ensure that routing changes do not affect downloads. Mid-term we have plans to simplify the routing logic and remove the confusing _:layerId portion of the URL.
Yes, that is the site we are having trouble with. I'll try making them private and then public; with respect to the gallery cards, this was generated via the dynamic gallery layout. I'm assuming that removing it and re-adding it would generate the URLs again so I'll also give that a shot as well. We do appreciate your help!