It comes from this blog: http://www.typemoon.org/bbb/diary/log/201506.html
My translation: I began by thinking that #25's script was "mostly original, so I should write this as a side story to the original [the VN] story." And so I, Kinoko, was at my wits end trying to write something approximating a screenplay.
I would like you to give me your translation of such sentence.
I'm particularly interested in the reference to the script and how it's supposed to be almost original. Any reference to that script (and where it comes from) I might have neglected is most welcome.
Edit: My translation wasn't very literal. Another approach would be something like:
The production of episode 25 began with "since it's mostly original content, it should first be written by the original author". And then the production team clutching their heads at the completed so-called script by Kinoko.
The question is the same.