Ktor not serving static images properly

Question

I have a ktor server, and I'm trying to serve some static assets that are stored in resources folder assets.

static("/assets") {
    resources("assets")
}

For .css files it works when I fetch them with something like http://0.0.0.0:7200/assets/css/main.css, but when I try to fetch images with http://localhost:7200/assets/img/flags/uk.png, it returns a broken image, although it exists.

I've tried different image formats and paths. Also tried different ways of serving the resources, but none worked.

Edit (Beginning of image downloaded from browser):

Edit (Beginning of original file, why are they slightly different?):