Continuity mistake: At the start of the episode when Tyreese and Carol are walking down the railroad tracks towards Terminus, they encounter a herd of walkers coming out of the woods. One of the first walkers to cross the tracks is a male walker wearing a burgundy sweatshirt with a rip in the middle. When gunfire erupts at Terminus, the walkers turn their attention towards it. In the next shot when they start to head towards the sound, we see the same male walker now in the middle of the herd yet to cross the tracks, next shot after that, we again see him at the front of the pack.
Visible crew/equipment: When Sam comes to visit Carol with items in his hand, he walks through the front door of the house. Carol shuts the door after she lets him inside. As she does this, you can see the reflection of a black sheet or tarp of some kind covering the door area where the camera reflection would be.
Continuity mistake: When Beth is looking for a key in Officer Dawn's office, she encounters Joan lying dead in the office from bleeding out, apparently from suicide with a pair of surgical scissors. Her left hand is covered in blood. But when Officer Gorman enters the room and Joan starts to turn into a walker, the blood on her hand has disappeared.
Continuity mistake: When Jessie hands a basket of stuff to Rick on the front porch the paper towels keep switching sides. First they're on her right, then when she hands the basket straight across to Rick they are on her left. Then in the next shot of Rick holding the basket they're back on her right.
Continuity mistake: Possible Spoilers! At the very end of the episode Rick walks up to the wall of Alexandria to check out a noise. When the camera shows the walker on the other side of the fence it is clear there is nothing else out there. When the camera shows the fence from behind Rick there is the roof of a house visible above the top of the fence. The shadows made by the struts of the fence make it apparent that if there was a house the other side of the fence would have been in shadow.
Continuity mistake: At the end 3 men go to rush Rick - the guy on the right is Glenn. All three men are standing shoulder to shoulder when Rick pulls his gun, and Glenn has disappeared. Cut back to Rick and a wide shot - no Glenn. Cut to a close up of the group and Glenn's back, but there is a big gap between him and the other two men. This scene is continuous - he hasn't got time to move.