I'm sure others have noticed either some plot holes or inconsistencies by now. I know there's a reason behind it because from what I've heard, it can be difficult to keep it consistently on every aspect.
Not only that, if anyone attended the 'Season 7 Finale: Director's Cut' panel back in October during Nightmare Nights 2017 (R.I.P) they'd most likely remember that someone asked 'Big Jim' a question really similar to yours.
He explained that it's been a miracle they've been able to be as consist as they currently are.
The thing you need to know is that not everything will be perfect, whether it's a T.V show, movie, or anything published or released to the public.
We're not perfect, and as Twilight and the gals quoted it perfectly, "We're not flawless".