Swagger/Swashbuckle showing "Unknown response type" - swagger

Question

I am creating an C# ASP.NET Core 2.0 REST API, all going well for the most part. It is using MVC routing to gen the REST API. The controllers are pretty simple.
// POST: api/Volume/{zoneID}/Set/{volume}
[HttpPost("{zoneId:int}/[action]/{volume:int}", Name = "Set")]
public IActionResult Set(int zoneId, int volume)
{
return CreateAndSend(strZonesLevel, zoneId, $"{volume:X2}");
}
Using the latest of everything, installed Swagger/Swashbuckle for AspNetCore 2.3.0 and the UI comes up with the APIs and all. The SwashBuckle UI works well, I can test the API etc.
The one exception is that on the UI, the Response type ALWAYS comes back as "Unknown Response Type."
https://i.stack.imgur.com/6qqBh.jpg
I have the following attributes in front of my class (all methods return the same type)
[Produces("application/json")]
[Route("api/Volume")]
[ProducesResponseType(typeof(ControllerResponseModel), 200)]
[ProducesResponseType(typeof(ControllerResponseModel), 400)]
[ProducesResponseType(typeof(ControllerResponseModel), 500)]
The generated JSON seems allright, the ControllerResponseModel is in the definition, and referenced in all the right places by the Volume API. Here is a subset.
{
"swagger": "2.0",
"info": {
"version": "v1",
"title": "AVController API"
},
"paths": {
"/api/Volume/{zoneId}/Set/{volume}": {
"post": {
"tags": ["Volume"],
"operationId": "ApiVolumeByZoneIdSetByVolumePost",
"consumes": [],
"produces": ["application/json"],
"parameters": [
{
"name": "zoneId",
"in": "path",
"required": true,
"type": "integer",
"format": "int32"
},
{
"name": "volume",
"in": "path",
"required": true,
"type": "integer",
"format": "int32"
}
],
"responses": {
"200": {
"description": "Success",
"schema": {
"type": "array",
"items": { "$ref": "#/definitions/ControllerResponseModel" }
}
},
"400": {
"description": "Bad Request",
"schema": {
"type": "array",
"items": { "$ref": "#/definitions/ControllerResponseModel" }
}
},
"500": {
"description": "Server Error",
"schema": {
"type": "array",
"items": { "$ref": "#/definitions/ControllerResponseModel" }
}
}
}
}
}
},
"definitions": {
"ControllerResponseModel": {
"type": "object",
"properties": {
"command": { "type": "string" },
"message": { "type": "string" },
"url": { "type": "string" }
}
}
}
}
Any ideas why the UI would not be showing the return type and value? I have tried numerous things, like using gets instead of posts as well as using the [SwaggerResponse] attributes, but the results are the same.

Answer 1

This has been identified as an Edge browser issue with Swashbuckle, not the code posted here. It is reproducible on many sites. Issue has posted on GitHub # https://github.com/swagger-api/swagger-ui/issues/4337