Hello @Martin Nielsen

I did some analysis about this. As of my understanding, I found this is because of the method DispatchRequest in the %CSP.REST. The below piece of code is actually skip your accountId due to forward your request to another "DispatchRequest" in the other dispatch class(for your case "AnotherController" class). But these are rewritten in IRIS already. You can try override this method for testing.

Set tMatchUrl=$Piece(tMatchUrl,tMatchcher.Group(1),"2",*),tForward=$LisGet(tMapEntry,3)

Actual Url: /1001/anothercontroller/001
Url after above line executed: /001

Hello @Sylvie Greverend

The sample swagger for produces "image/jpeg" and consumes "application/json" and "application/xml" for sample. Once the spec.cls. Once it's complied it creates a "DownloadImg" classmethod in .disp.cls

swagger

{
	"swagger": "2.0",
	"info": {
		"title": "test",
		"version": "1.0.0"
	},
	"paths": {
		"/Test": {
			"get": {
				"summary": "Test download",
				"operationId": "DownloadImg",
				"produces": [
					"image/jpeg"
				],
				"consumes": [
					"application/json",
					"application/xml"
				]
			}
		}
	}
}

Generated class method

ClassMethod DownloadImg() As %Status
{
    Try {
        Do ##class(%REST.Impl).%SetContentType("image/jpeg")
        If '##class(%REST.Impl).%CheckAccepts("image/jpeg") {
            Try {
                Do ##class(MyLearn.LearnREST.Swag.impl).%ReportRESTError(..#HTTP406NOTACCEPTABLE,$$$ERROR($$$RESTBadAccepts))
            } Catch {
                Do ##class(%REST.Impl).%ReportRESTError(..#HTTP406NOTACCEPTABLE,$$$ERROR($$$RESTBadAccepts))
            }
            Quit
        }
        Set response=##class(MyLearn.LearnREST.Swag.impl).DownloadImg()
        Do ##class(MyLearn.LearnREST.Swag.impl).%WriteResponse(response)
    } Catch (ex) {
        Try {
            Do ##class(MyLearn.LearnREST.Swag.impl).%ReportRESTError(..#HTTP500INTERNALSERVERERROR,ex.AsStatus(),$parameter("MyLearn.LearnREST.Swag.impl","ExposeServerExceptions"))
        } Catch {
            Do ##class(%REST.Impl).%ReportRESTError(..#HTTP500INTERNALSERVERERROR,ex.AsStatus(),$parameter("MyLearn.LearnREST.Swag.impl","ExposeServerExceptions"))
        }
    }
    Quit $$$OK
}

Some useful links 

HTH.

Hello @Sylvie Greverend 
Using the Oauth tokens "Bearer tokens" instead of basic for Authorization is another way to handle it.

Hello @Scott Roth 

Did you get a chance to check the ^ISCLOG global for Http request logging. Because configuration done int ^%ISCLOG and logging was written in ^ISCLOG

^FSLOG for internal FHIR server logging 

Thanks!