I have experienced a strange behavior with my Web Map in ArcGIS Enterprise 10.7.1.
I have couple of Web Maps configured and Web Apps on top of them. Each Web Map has a long list of feature layers coming from different sources (hosted feature layers, feature layers from ArcGIS Server, WMS services, etc..) and having different coordinate systems. While configuring these Web Maps I was using the same basemap with wkid 32633. Now I want to change to another basemap which has wkid 25833.
When I go to Map Viewer and choose a new basemap from the gallery, feature layers become grayed out. When I save the map, the feature layers disappear. However, when I add feature layers again, they come up on the Web Map without any problems. What is more interesting, it happens only for some of the Web Maps. Having two almost identical Web Maps, with the same basemap, I am able to change to the new basemap without any problems on one of them, but the other one experiences behavior described above.
Since I have Web Apps with many widgets on top of the Web Maps, removing layers and adding them again is not the best solution as I need to configure most of the widgets from the scratch.
I would appreciate any help and explanation what is happening in background of my Web Maps.