I have an update to that!
In my own project the WaterPlane_Blueprint is editable.
and I can open the waveworks_watr_plane_map
only thing is the water is not rendering, had no time to further invetigate that so far.
But I think the reason why works in my project without a crash is that I needed to add RHI to my public dependency modules to the MyProjectName.Build.cs file.
PublicDependencyModuleNames.AddRange(new string] { “Core”, “CoreUObject”, “Engine”, “InputCore”, “RenderCore”, “RHI”, “D3D11RHI” });
Probably necasary now because of a change in the API structure form .19 to .21!?