It is the little things, the details that make a story believable. And just as easily, make it unbelievable.
Fiction is all about making up stuff and getting other people to believe it is real enough to keep reading. Even better, if they tell their reading friends that they HAVE to read your book.
Some of the detail errors are sloppy self-editing. There is a group of people in the room. Character A leaves. A conversation, or dialogue ensues. Character A leaves the room.
Now, either the writer forgot to put them back in the room or they left twice.
I think that stems from not paying attention to the story when writing; stopping in the middle of a scene or going back to add something without noting what was already written.
Another deadly detail is not putting in correct details when writing about a real place. For example if someone wrote about Phoenix in the summer and stated that Character A was parched and went to the hose for a cool drink, the natives would know that isn't possible.
In the summer, warm water comes out of the hose. When it is 110 F outside, there is no cold or even cool water unless refrigerated. When doing laundry there is no such thing as the cold setting in the summer. The cold water comes out warm.
Every real location has distinct characteristics; things that anyone who had been there would notice. At the ocean, the air is moist and there is a distinct pattern to the breeze depending on the difference in the ocean and land temperatures.
If it is a fictious location, then the characteristics have to be consistant, and if not, the writer has to note the significance of the difference.
In high school we had a writing assignment, fiction, I suppose. The student questioned why the teacher had marked off points for the character's name when the student had made up the name. The teacher said, "Yes, but you spelled it three different ways for no reason."
Our readers deserve a well written story. Try not to self-edit with the telly on. Make notes to refer to when you make up something, like a name, a holiday, or land mass. Pay attention to the details. Anything about a walk along the beach that doesn't mention the damp breeze will get my attention. That makes believability take a hit. Enough hits, and the book doesn't get read all the way through.
Do your best work. Write right.