Noting continuity issues is a big part of a copy editor’s job. Not just timeline continuity, making sure the author stays true to the days of the week or any mention of time passing, but also continuity within one scene.
For example, if a character enters a room and stands talking to another character, then several pages later, the author writes, “He stood…” readers will stumble if they didn’t know when he’d sat down. The last time they “saw” him, he was standing. Readers might even shuffle back through pages to see where they made a mistake and missed the author’s reference to him sitting down. I know I’ve done that, as a reader. I want to keep an accurate picture of the tale unfolding in my head.
Does this mean an author has to describe every action in a scene? No.
There are ways to skip ahead through actions so that readers will still be able to visualize what went on. For example, if the author writes that “Jane went out to her car,” she doesn’t need to then tell the reader Jane puts the key in the ignition, puts the car in Drive, steps on the accelerator pedal, signals her turn out of the driveway, and drives off down the road. She can skip those steps with a quick time lapse reference, such as “Once on the road, Jane looked in the rearview to see if she was being followed.” That simple “once on the road” covers all the other steps in between.
That said, knowing what to include and what to leave out can be tricky. I know some authors might think it is nitpicking to point out the need to tell the reader when something simple happened, especially if it’s in a series of everyday actions; but your goal has to be to keep the readers from stumbling and rewinding their images.
If Jane is running out the door, for example, and later in the scene you mention her hugging her coat tight…readers might have to rewind their image to include Jane grabbing her coat before she ran out the door. They might have envisioned her racing so quickly, she forgot about a coat.
So, that has to be your goal: to keep the reader from doing the mental rewind as she realizes, oh, Jane had her coat, or Jane was sitting, or Jane made dinner after pulling those steaks out of the fridge and before everyone sat down, fork in hand, at the table…
Think of the reader’s immersion in your story as a film playing in their heads, and every time you cut away to a new action, you need to make sure they envisioned the right activities in between and weren’t left guessing when such-and-such took place.