Frances Conroy ("Old" Moira O'Hara) is right-eye dominant. Many times you can see that she, as Moira, is focusing on the object she's looking at using her "blind" right eye instead of her left eye.
During Roanoke's second half, the characters are seen using their camera-only phones for both constant recording and a flashlight - some episodes have them using their phones for days without charging them. This incessant use would wear down the battery within a few hours, even without using other apps.
Throughout season 4, ETC Source Four lighting fixtures can be spotted hung above the Freak Show stage. The Source Four wasn't manufactured until 1992, 40 years after the season is set.