Internment - S4-E5
Continuity mistake: When Rick gets out of his car and talks to Maggie inside the prison gates. The car door opens and shuts throughout the conversation.
Internment - S4-E5
Continuity mistake: In the previous episode, Rick and Carol are shown hunting through houses for household drugs to fight the flu. They even make a mention that most of what they find expired a year ago, but to bring it back to Hershel anyway, and let him decide about it. But in this episode, Rick returns, talks to Hershel, and no mention is made about him bringing medicine. Considering how important it was to fight the flu with any means possible, Rick would not have let Carol drive off with the potentially life-saving drugs.
Answer: Walkers are attracted to noise, they can tell who's dead and who isn't dead, in S1 when Rick and Glenn cover themselves in walkers' guts they're able to get far by walking through the herd of walkers because they smell like they're dead, but as soon as the guts get washed off by the rain the walkers immediately attack them, if you draw attention to yourself they will attack you which we've seen that many times throughout the series that it's not always successful. Whether you're covered in guts hiding under dead corpses or under a car.