When Ben is pleasuring himself near the window after seeing Moira, the curtains are closed at first, but when the camera cuts to his head the curtains are open.
Vivian gives Ben a long cut on the left arm after she catches him committing adultery. But every time we see his arm during the rest of the show, there is no scar.
When Ben goes to light the fireplace, he turns the gas valve clockwise. Gas valves, as with all valves, open counter clockwise.