If the author doesn’t follow their own script that is a big turn off. Realism is key for me to enjoy any movie/story otherwise I’m distracted backtracking to see if I missed something or if it was a misread on my end. One story I stopped reading had a group scene but half way through one of the participants removed his clothes for a second time in the same session.
I enjoy a good story that build some momentum and even better if it has some well placed surprises.
The other annoyance that I can often overlook but sometimes it will cause me to lose interest is when a long story especially a series ALWAYS has porn star supernatural orgasmic characters in every scene. After a while I’m just wondering how this fellow is finding the fluid to cum for the 5th time in a session all the while the women involved seem to scream with orgasm every time they are touched.