Bug Ghosts Editor instances (since 2021.3)

Hi, I didn't notice this before (I was using 2021.2.latest)
I often get instances of Unity Editor + Crash handler fully using a hardware thread in background.

The repro is :
Having a VS2019 IDE open with the current projet opened in Unity
In Unity goto Project/some folder containing .cs
Make a copy of a .cs file, then rename it
(that's the way I create a new .cs file to be automatically updated in VS project)
The fan of your notebook starts noise
Going to Task manager you will notice a running Unity instance (in my case using 1 GB + 40% CPU)
and another Unity instance (using 600MB + 25% CPU)
do another .cs copy/rename => a third unity instance (using 600MB + 25% CPU)

Exit the visible running Unity instance : fan stops blowing, all unity instances are gone