I tried to reproduce this issue but couldn’t are you opening up the chat window as a popout window? How are you closing the chat? Is it possible you just need to click on the meeting window again?
I tested this on the latest version by the way. Can you try to update?
I am seeing what you are seeing, but I believe this is intended behavior since the Zoom client app has the same behavior. You can get around this by using alt+a instead of the spacebar.