Cannot run twice; Unity crashes after running more than once #701

Environment

• Pythonnet version: 2.3.0 py35
• Python version: 3.5.4
• Operating System: Windows 10

Details

I want to run this code on my Unity project:

using Python.Runtime;
using UnityEngine;

public class TestLib : MonoBehaviour
{
    // Use this for initialization
    private void Start()
    {
        print("initializing python");
        PythonEngine.Initialize();
        print("running python code");
        using (Py.GIL())
        {
            dynamic np = Py.Import("numpy");
            print(np.cos(np.pi * 2));
        }

        print("Destroying python engine");
        PythonEngine.Shutdown();
    }
}

Here's the output:

It's able to run once but when I try to run it again, Unity editor crashes.

Here's the entire process:
I open Unity. Inside it, I click play to run this code, it works. And then I stop, and then I run the code again, Unity crashes.

Reasoning

• I'm suspecting that it's because python is still running in the background when I stop the game session.
  But I tried Initialize() and Shutdown() twice in the code and it works (if I run it once). So I think it's not shutting down issue. It's something else that I cannot figure out.
• This error depends on the python code for sure. If I remove the python part and run, it would be able to run as many times as I want.
• It might also be a threading issue which I don't understand.

What are the possible causes and fixes?