Plot hole: It's been established that if you die on the property, you remain as a ghost for all of eternity. However, in Season 8, Moira's bones are retrieved and buried in a cemetery so that her ghost can escape and join her mother. However not all the ghost's bones are buried on the property, we know for sure that the Black Dahlia was not buried on the property and it's not likely Tate, Vivian, Ben or some of the others are buried on the property as well so they should not be tied to the house.
Suggested correction: Tate's victims from the school shooting are ghosts who can move between different locations. There's nothing to suggest that the ghost of the Black Dahlia isn't merely choosing to be in the Murder House rather than being tied to it. The same goes for Vivien and Ben, since Violet is going to stay in the house, so might they.
Deliberate mistake: Conjoined twins Bette and Dot have freckles and moles on their faces and necks in the exact same places.
Suggested correction: Not technically a mistake; unlike regular twins, conjoined twins are always identical in appearance, contrary to what movies/TV suggest. This could easily include mole patterns.
I looked up "conjoined twins" on Google images, and there are numerous photos of conjoined twins having freckles and moles in different spots. Notably on the Hensel twins, Brittany has a mole on her chin, but Abby does not. This disproves your suggestion that conjoined twins are always identical in appearance and could have identical mole patterns.