Too Far Gone - S4-E8
Continuity mistake: When Hershel crawls away and the fight begins, in the long shots of the governor's men Hershel's body can not be seen next to the cars, this is from all angles.
Too Far Gone - S4-E8
Continuity mistake: After The Governor shows up at the prison with his arsenal, Hershel and Michonne are taken out of the vehicles and placed kneeling on the grass side by side, about 1 arm's length apart from each other. But when Rick makes his way down to the fence to talk with The Governor, Hershel and Michonne are now about 4 arms' lengths away from each other. This goes back and forth for a few shots.
Too Far Gone - S4-E8
Continuity mistake: When the Governor and his group show up and bomb one of the guard towers to get Rick and his group's attention, when Rick first runs outside the guard tower on the far left is on fire, but when Rick walks down to the fence to talk to the Governor the guard tower in front by the front gate is the one on fire. And it switches back and forth between the two. (00:16:05 - 00:19:15)
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