Publishing .NET Core 3.1 React application on IIS 8.5 results in API routes not being respected - asp.net-core-mvc

Question

I'm currently trying to mount a .NET Core 3.1 MVC application created with dotnet new react. The application works perfectly fine when running it via Visual Studio Code. However, when publishing with dotnet publish -c Release -r win81-x64 and mounting the application in IIS 8.5, the routes for the APIs stop working, sending all requests to the React page.
Currently my configuration in Startup.cs looks like this:
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
else
{
app.UseExceptionHandler("/Error");
// The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
app.UseHsts();
}
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseSpaStaticFiles();
app.UseRouting();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllerRoute(
name: "default",
pattern: "{controller}/{action=Index}/{id?}");
});
app.UseSpa(spa =>
{
spa.Options.SourcePath = "ClientApp";
if (env.IsDevelopment())
{
spa.UseReactDevelopmentServer(npmScript: "start");
}
});
}
And the code in a test controller I made looks like this:
namespace Application.Controllers
{
[Route("api/[controller]")]
[ApiController]
public class TestController : ControllerBase {
private readonly ILogger<TestController> _logger;
public TestController(ILogger<TestController> logger)
{
_logger = logger;
}
[HttpGet]
public async Task<ActionResult<string>> GetTest()
{
return "Test";
}
}
}
I also tried creating a new React project and mounting it, and that does seem to work. However, the Startup.cs file has the exact same configuration, so I can't find anything to modify on my application.

Answer 1

I figured it out. Turns out the first version I uploaded had some issues that prevented routes from working properly, and while I immediately fixed it, the Service Worker that the default .NET project has cached the broken API point as part of the site. Apparently this bypasses having the 'Disable Cache' tick box in developer tools.