When Sasha is looking for Dr. S., she stumbles into the cell block after opening the door. When the camera switches from behind her to in front of her the door goes from being opened to closed.
The name at the top of the list of "antibiotics" that Daryl has been given is Zanamivir which is an antiviral, not an antibiotic. Zanamivir by the way would be more useful for treating people during an outbreak of flu.
A group head out to find medication to treat the flu outbreak and they have been told to get antibiotics. Antibiotics treat bacterial infections NOT viruses such as the flu. The group should be looking for antivirals.
When the group is fighting the zombies on the road, as a spray of blood shoots across the other zombies, one, a woman, flinches.
At the end of the scene at the campsite in the woods when Carl and Herschel turn to leave the bear trap zombie behind, there is a figure that clearly hides behind a tree in the distance, presumably a crew member.
When the infected are put into quarantine, they are locked up together in one big room. Consequently, if one of the infected dies and turns, the other infected would be at risk of attack, despite the group looking for a cure.
Hershel says his is going to pick elderberries to make tea for the sick people,
the plants that Hershel is picking berries from in the woods don't resemble elderberries.
When the group is discussing the trip to the veterinarian school, Hershel stands up from the table with both legs intact.