Continuity mistake: When they get back to the community after stealing all explosives from the road, the Saviors show up and search for Daryl. When they do, that's when they show a one-second clip of the guy Dwight killed a few episodes back, the guy who said there was nothing to go back to. The guy is then shown to be a walker in the defense yard of the Saviors. So, how is he shutting the van doors of a vehicle in this episode? (00:43:12)
Other mistake: When the Alexandria Group are at the Hilltop trying to convince Gregory to join them in their fight against the Saviors, we can see the actresses who play Michonne and Maggie trying to hold in their laughter. (00:06:02)
Revealing mistake: When the two cars drive down the freeway with the cable in-between them, there is no blood or body parts on the cars at the end despite the carnage, suggesting CGI effects.
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.