HttpClient with SocketsHttpHandler re-uses client certificate of different instance

[Sebazzz]

I have a HttpClient I setup using client certificates using SocketsHttpHandler. These run in several tests in my integration test suite. However, in one test I test the behaviour when no client certificate is configured: In that case, a client certificate from a different test and thus a completely different HttpClient is sent.

Is this known behaviour?

 handler.SslOptions.ClientCertificates = null;
handler.SslOptions.ClientCertificateContext = null;
handler.SslOptions.LocalCertificateSelectionCallback = (sender, host, certificates, certificate, issuers) => {
                // No client certificate provided
                TestContext.Progress.WriteLine("No client certificate provided in selection callback.");
                return null;
            };

I see "No client certificate provided in selection callback" printed to the test output - yet that connection comes in with the client certificate from the different test.

[Sebazzz]

Anyone?