Continuity mistake: Arriving at Alexandria, Rick is shown from an interior POV leaning into the back of the car and picking up Judith, who is mostly wrapped in a spotty shawl. As he is shown doing this from an exterior POV, the shawl is barely visible, bunched up behind her legs. (00:41:44)
Continuity mistake: When Jessie brings a basket of stuff to Rick the paper towels are on her right, then when Rick takes the basket they're on her left, and then in the next shot 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. (00:48:00 - 00:50:00)
Other mistake: Earlier in the season Father Gabriel Stokes burns his clerical collar, but in the end of this episode he is wearing it again. Especially doesn't make sense, because he said he gave up being a pastor.
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: Sasha is pinned by the walker, but saved by Michonne. As she is standing up, the leaves in her hair disappear between shots.
Continuity mistake: At the end of the previous episode, Daryl leaves on a motorbike with a car following. In this episode Daryl's still out but no bike - he's in a car. It's a continuous trip with the bike he built at the compound.
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.
Other mistake: When Gabriel is out by himself on the road and kills two walkers, he is wearing a white shirt. Blood is shown spattering everywhere, but his shirt remains spotless. (00:37:00 - 00:39:00)
Revealing mistake: When Rick checks his revolver before holstering it, there are no primers in his cartridges.
Continuity mistake: When Aaron and Daryl are stuck in the van surrounded by walkers, he lights up a cigarette with a yellow filter and it changes to a white filter as he starts smoking it.
Other mistake: When Nicholas shoots himself, both him and Glenn fall with their feet facing the dumpster, and their heads facing the walkers. However, when they cut to the shot of presumably Nicholas being eaten, we see Glenn's head facing the dumpster. This does not make any sense. Glenn would have had to do a complete 180 turn before landing, or move around without being detected by walkers. In fact, the way they landed does not make sense at all. The fence seen when Glenn and Nicholas climb on top has also disappeared.
Revealing mistake: When Aaron is pinned down by the sewer zombie, the zombie actor's neck can be seen below his head mask.
Suggested correction: I went back and watched this scene several times, and I think the OP is mistaking Aaron's hand on the Walker's neck as the gap in the mask.
Continuity mistake: In the scene in the garage near the beginning of the episode where the characters are gathering supplies, the sun is on them in one shot. In the reverse shot, they are dark and the sun is no longer shining into the garage. Then back to them, it is again.
Factual error: In the opening scene and throughout, young Sam Anderson, cloistered in his bedroom, is presumably listening to a crackly 45 rpm copy of Nick Lucas crooning his 1929 hit, Tiptoe Through the Tulips. In reality, the disc with gold/blue label spinning on Sam's turntable is not the song playing. The original Tiptoe was released in 1929 on 78 rpm vinyl by Brunswick Records, and was finally pressed on vinyl 45 by Accent Records in 1974 (solid robin egg blue label however, not gold/blue).
Continuity mistake: The Wolf is shown to have filthy teeth but when Carol confronts Morgon in The Cell, his teeth are clean.
Plot hole: Diana in her final scene is seen shooting her last bullets at the walkers that are offscreen, moving toward her, so suicide was not an option, meaning the walkers would have eaten her until she died, becoming a walker. And yet her body is completely clean when her son and Michone discover her in walker form. Blood free (even on her clothes) and fully intact, no chunks of her missing, no bite marks.
Knots Untie - S6-E11
Continuity mistake: When the bus gets stuck in the mud, the team leaves the vehicle. However, their shoes/boots are already covered in mud despite having not left the bus yet. (00:17:50)
Continuity mistake: When the sodas are retrieved from the cool box there are 6 cans, but when the angle changes there are only 4.
Revealing mistake: When Morgan stabs the walker which is hanging from The Tower, the blade enters its lower head, but the blood can be seen coming from above the hairline. (00:25:30)
Suggested correction: I can see where the confusion is. If you watch it normal time, it looks like he stabs him in the cheekbone. But in slow motion, you can see the blade go into the top of the skull.