1) What happened
The Editor hangs after the MD attaching.

2) How can we reproduce it using the example you attached.
Faced during FTP, case "Attach the MD debugger to a Unity project while in playmode".
Steps:
1. Open attached project in Unity
2. Select the scene
3. Open CSharpScripted.cs
4. Attach MD to the Editor
5. Set breakpoint on one of the methods, e.g. Awake or Start
6. Switch to the Editor and play the scene.
Expected:
The execution is interrupted on the breakpoint.
Observed:
Nothing happens in the MD, the Editor looks hanging and doesn't respond to an input, Activity monitor shows it as not responsive.

Unity hangs when
1. MD is attached to the Editor.
2. The play button is pressed.

If the play button is pressed before the MD attaching, everything goes as expected. So we have the workaround but still it's impossible to debug some events like Awake, OnEnable, Start.