Hello.
I just downloaded 4.0 beta 6 windows 64 from official download page, now the editor or the project I am using will freeze for a few seconds upon exit or manually close via 'x' button.
So I just switched back to 4.0 beta 5 with the same computer and same project, the problem vanquishes.
I noticed the whole computer is freezed like CPU is using up to 100%, even the mouse cursor is freezed for a few seconds, as if you are running a fully-load machine learning or video encoding that eats up all you CPU power.
Specs is not an issue since I also do some small unity and unreal engine 5 stuff every now and then.