I had the same problem, and after hours of tryng to set the correct uft format in dockerfile configurations and json serialisation, i just try to recreate the file and work... in my case the problem was the encoding type that visual studio save the .cs file. The visual studio dont show the ending type, however when you open the file in vs code will show in footer "UTF-8", then when i recreate the file is "UTF-8 with BOM" the magically work, even in alphine....