I would say in your settings.json, you should only specify cssFiles, no scss files.
The css files should be compiled automatically by Mendix from your scss files.
So, my settings.json looks like this:
{ "cssFiles": ["theme.compiled.css"]}
A file I don't see, but is generated in the deployment folder as soon as I deploy.
Maybe this helps!
"pageTemplates": "WebModeler",
"cssFiles": [
"styles/web/css/main.css",
"styles/web/sass/app/_custom.scss"
],
I have cssFiles include the _custom.scss, and have _custom.scss file in that location. When I check the browser, _custom.scss doesn't have any code.