Indifference - S4-E4
Visible crew/equipment: During the scene where Daryl's group finds the auto shop, Daryl spits on his hand to wipe the window and is surprised by a zombie banging up against the window. He says, "Got some friends inside" and walks away. The camera pans to the window and a crew member wearing a white hat and (what appears to be) an orange shirt is visible in the reflection. He seems to be taking a picture (probably for continuity, which is pretty ironic). (00:09:50 - 00:33:05)
Answer: The walkers could have knocked them down more than once. There may have been another wave that knocked down the fence earlier and they're going to put it up again soon.
Captain Defenestrator