Can't connect to Windows 2019 Server via SSH

My configuration looks like this:

Gitlab 12.3.5 CE runs on a Debian, Windows 2019 with OpenSSL and an installed Gitlab runner.

Since the newer Windows 2019 versions are delivered with optional OpenSSL, the connection via SSH is possible without any problems (tested via console).

The .gitlab-ci.yml is quite simple:

stages:
  - test

rollout_javahost:
  stage: test
  script:
    - echo "hello"
  tags:
    - ssh-windows-server

The config.toml contains the following:

[[runners]]
  name = "SSH Access Windows Server"
  url = "https://gitlab.domain.eu/"
  token = "_token_"
  executor = "ssh"
  [runners.ssh]
    user = "username"
    password = "pass"
    host = "ip"
    port = "22"
  [runners.cache]
    [runners.cache.s3]
    [runners.cache.gcs]

If I run the pipeline I get the following error:

The command "$'bash'" is either misspelled or could not be found.

For the sake of completeness the German error message:

Der Befehl "$'bash'" ist entweder falsch geschrieben oder konnte nicht gefunden werden.

I wonder why the SSH connection fails, although it is not a problem via console. Are there other ways to debug the connection?

I am grateful for any help.

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