Generating a string resource entry in a resource file (Resources.resx) and deleting the entry again by the VS string resource editor results in a corrupted .resx file. The resource editor reports 'ResX file Data at the root level is invalid. Line 1, position 1, cannot be parsed.'.
This can be reproduced by creating a small C# console application:
Add a string resource manually ("Hello1").
Insert a string literal in the Main method of Program.cs: Console.WriteLine("Hello2");
Use the CodeRush for Roslyn 'Extract String to Resource' refactoring tool and convert "Hello2" to a string resource.
The program compiles without errors and behaves correctly.
After deleting "Hello2" again, the Resources.resx file is corrupted, compilation is not possible.
It does not happen when deleting the manually added entry "Hello1".
I could reproduce this behavior with Visual Studio 2015 and 2017.