tmux loses ability to input text after I close the terminal where it was initiated

Question

tmux acts strange after I close the terminal it was initiated and reattach again.

Basically, I do is:

1. start the iTerm or Terminal
2. start a new tmux session
3. work inside tmux
4. close the terminal
5. open a new terminal
6. attach to tmux session

After the step 6, tmux starts to act strange, it won't react to keystrokes however it still listen to and respond to tmux commands.

Then, if I create a new window navigate back and forth tmux appears to dump all the content I've previously typed.