session locked

Hello, Sir,

Thank you very much for developing this great great software!

[1]
Recently, I found that when I tried to evaluate several source blocks (same session name)
of the whole buffer. The Emacs got locked.

I used below command:
C-c C-v b or C-c C-v C-b org-babel-execute-buffer

[2]
Then I restarted the Emacs ob-ipython, the same code block cannot be evaluated by
using C-c C-c.

After some trial and error, I found that the solution is to rename the session.
It seems that a session name is failed forever once I tried the C-c C-v b.
The error message said there is some issue with the tornado serve.

[3]
It is not a big deal for my usage.
The above information may be helpful to others having same issue.

Thank you