App URL setting broken for .NET Core 2.0 projects in Visual Studio 2017 15.5.0

I recently upgraded Visual Studio 2017 to version 15.5.0 and later on to 15.5.1.

So far everything was working fine developing .NET Core (2.0) web apis but after the updates the problems started. The problems occur on existing projects as well as newly created ones.

Problems: Sometimes I receive the error message:

Unable to start process C:\Program Files\dotnet\dotnet.exe. The web server request failed with status code 500, Internal Server Error. The full response has written to C:\Users\username\AppData\Local\Temp\HttpFailure_04-01-08.html

This hidden directory is a great place to store error files by the way.

If i look into that file I can read:

HTTP Error 500.19 - Internal Server Error

Module: IIS Web Core Notification: Begin Request Error Code: 0x800700b7 Configuration file: \?\C:\solution\project\web.config

configuration source

<handler>
 <add name="aspNetCore" path="*" verb="*" module="AspNetCoreModule" resourceType="Unspecified" />
</handler>

It seems to automatically add the add-tag on start even when I delete it.

So far, deleting the .vs directory up and on seemed to help against this but this shouldn't be a permanent solution.

The second (and more blocking problem) that occured is that the APP URL setting seems to be broken somehow.

For testing this bug I created a new Web API project (with the values controller) and added and configured swashbuckle.AspNetCore to show the UI for the ValuesController.

The default route for the values controller is api/values.

When I now configure the App URL settings in the project properties to start at http://localhost:50000/swagger the browser opens and shows the wrong url, namely http://localhost:50000/swagger/api/values with the correct response of the ValuesController but not the swagger ui. At this point it shouldn't have the extension /api/values since it is not configured and I don't know why or where this is added (it's not in the configuration).

If I now enter (without stopping the app) http://localhost:50000/swagger I start receiving 404 errors an urls, even on http://localhost:50000/api/values.

Anyone else having this problem?

Anyone knows a fix for that?

Anyone knowing what is happening there and what the problem could be?