Text on video sites

Recently, when I was watching videos on video sites, I noticed that text is displayed at the bottom of the screen. While I was watching one movie, I could understand the content, but I couldn't really explain the grammar so I asked one of the staff.

According to the staff, it was indeed grammatically incorrect. It was incorrect, but the text was "correctly" displayed.

Computer doesn't make any mistake. I have a mixed feeling about this...

Above is translation of an article "動画サイトのテキスト" dated October 16, 2017

Translation by Hiroko Matsuda