When Lucius ventures into the woods he picks a branch off a bush with red berries on it. When he emerges out of the woods there are green leaves on the branch which were not there when he picked it.
After Ivy falls in the hole she puts the things she is carrying very near the hole, at the edge. When she is climbing out, the things have disappeared from the edge, and once she is out, they are a few meters from the hole.
The mud on Ivy's yellow cloak in Covington Woods keeps changing between shots.
During the wedding feast, two villagers throw a carcass onto a stone slab at the edge of the village as an offering to "those we do not speak of". The carcass appears topside-down after it is thrown. However, when viewed from the other direction in the next shot, the carcass is topside-up.
As Ivy listens to Mrs. Clack ask the villagers to offer Lucius their prayers, Ivy is standing at a distance from the crowd. In the next shot she is standing much closer and is now slightly behind them.
When Ivy enters the woods to get help for Lucius, off in the distance through the trees you can see a pole with a bell on it, used by the villagers for warning purposes. This has been mistaken for a telephone pole and the bell as a transformer.
During the first alarm set off by the tower watchman, the village is in a frenzy to hide in their homes but Lucius is walking around. On the corner of a house, before Lucas comes into frame (31:43) a forbidden-colored (red) bucket is clearly left on the porch.
Ivy is told to follow the hidden road, but not which way to go.
When the creatures first raid the village and Kitty takes the children to the cellar, there is a quick shot of Ivy at the door as Kitty begs her to close it and hide with them. A boom is just barely visible lifting out of the frame on the right side of the frame.
At the wedding dinner there is a child wearing red when red is the "bad color" and represents evil, yet nobody gets upset.