Cant' create content

I have…

I’m submitting a…

  • [ ] Regression (a behavior that stopped working in a new release)
  • [ ] Bug report
  • [ ] Performance issue
  • [x] Documentation issue or request

Current behavior

When trying to create a content with IContentsClient we always get

Squidex.ClientLibrary.SquidexException: ‘Squidex Request failed: {“message”:“Validation error”,“traceId”:"|b136944e-44350852ca9a6c71.2.ec9294ee_",“type”:“https://tools.ietf.org/html/rfc7231#section-6.5.1",“details”:["Request body has an invalid format.”],“statusCode”:400}’

Example code:
private readonly IContentsClient<Test,TestData> _testClient;
_testClient = clientManager.CreateContentsClient<Test, TestData>(“test”);

    public async Task CreateTest(TestData testdata)
            {
                await _testClient.CreateAsync(testdata);
            }

public sealed class Test : Content<TestData>
    {

    }

public class TestData
    {
        public string Bezeichnung { get; set; }
    }

Expected behavior

Content “Test” will be saved.

Minimal reproduction of the problem

Environment

  • [ ] Self hosted with docker
  • [x] Self hosted with IIS
  • [ ] Self hosted with other version
  • [ ] Cloud version

Version: [VERSION]
4.7.6.0

Browser:

  • [x] Chrome (desktop)
  • [ ] Chrome (Android)
  • [ ] Chrome (iOS)
  • [ ] Firefox
  • [ ] Safari (desktop)
  • [ ] Safari (iOS)
  • [ ] IE
  • [ ] Edge

Others:

Have you read this: https://docs.squidex.io/02-documentation/software-development-kits/.net-standard#why-no-code-generation ?

Thanks a bunch for the hint!