When Karen sees the picture of Gosnell at Schoonover's house, his bandage is over the left side of his face. When she flashes back to seeing him dead at the pier, his scars are on the right side of his face.
Despite the large gash in Elektra's arm that was hand-sewn just a few episodes before, her bare arms are both smooth with no sign of any scar.
During the opening fight scene between Elektra and Stick at the 4:30 mark, you see Elektra swing downward with her sai and get snagged in a book on the shelf. It's a blink and you'll miss it shot, but if you pause it at the right moment you'll notice the book is already slashed where the Sai is supposed to land.
When Frank takes the colonel into the woods and after Karen tries to talk him out of killing him a crew member can be seen in the background next to the cabin when Frank closes the door and says to Karen "I'm already dead"
At 15:34- Daredevil's right boot-lace is untied.