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An interactive session is held by GNU screen that captures the escape sequences starting with CTRL thus stealing the emacs focus.
To circumvent this, here's a nice page: https://www.emacswiki.org/emacs/GnuScreen
In my opinion the best solution is to sacrifice the escape sequence Ctrl+J which sends a sequence that is interpreted as the enter button, but the enter button does not send the same sequence.
edit (create if not exists) the file ~/.screenrc
:
# Use CTRL+j as escape sequence escape ^Jj # break screen flow in favor of emacs' one defflow off