@medigoth I know that feeling. Got badly ding'ed by TurnItIn once and it was because, while I included a citation for the source in the beginning of the paragraph, I didn't realize I had to keep citing it throughout that same paragraph. I forget what citation format style the teacher had us using though. It's been a while.
@ElemWiz I'm really, really glad I did most of my schooling before that was a thing. My dissertation work happened about the time Turnitin et al. were getting big, but if anyone ever ran that through plagiarism detection software, I didn't know about it. Students and professors both have reason to be paranoid these days, and that's not good for anybody. Except the companies making bank on proprietary black-box crap, I guess. 😕