Post FromBody not working without trailing slash

Question

I have an ASP.Net Core 2.0 Web API project that utilizes NSwag to get Swagger functionality. The problem is that when I use the SwaggerUI to test the API, the FromBody parameter is not working. However when I use Postman with the same body and application/json selected for the header (as in SwaggerUi), everything works.
In the debugger I noticed that the requests from Postman have a trailing slash, while the requests from SwaggerUi dont.

Here is the action from the controller:

[HttpPost("")]
[SwaggerResponse(HttpStatusCode.Created, typeof(BlobItem))]
public async Task<IActionResult> Create([FromBody] BlobItem item)
{
    if (item == null)
    {
        return this.BadRequest("the item is null");
    }

    var blobItem = await BlobHelpers.PostBlobItemAync(this.container, item);

    return this.CreatedAtRoute("GetBlobInfo", new { blobName = item.Name }, blobItem);
}

Postman -> item is filled
SwaggerUi -> item is null

---

I tried adding a trailing slash to the default route in Startup

app.UseSwaggerUi(typeof(Startup).GetTypeInfo().Assembly, new SwaggerUiSettings()
{
    DefaultUrlTemplate = "{controller}/{action}/{id}/",
    DefaultPropertyNameHandling = NJsonSchema.PropertyNameHandling.CamelCase,
});

without success and also

services.AddRouting(options => options.AppendTrailingSlash = true);

in Startup.ConfigureServices without success, meaning that the request still does not have the trailing slash through SwaggerUi.

---

How do I enforce trailing slashes or can I do something else to make sure that the FromBody parameter is working?