Continuity mistake: During a fight with Gregory, Maggie's right cheek gets cut and blood runs down her neck, but the next day talking to Rick her right cheek shows no sign of ever being cut.
Continuity mistake: Maggie comes over to Rick's porch to chat about the group not being whole. When she arrives the sun is going down. She even says something about putting kids to bed. Near the end of the scene there is a closer shot of her and it is afternoon.
Chokepoint - S9-E13
Audio problem: Lydia is hammering a nail in a board trying to barricade a door. The sound of the hammer hitting the nail is slightly off.
Visible crew/equipment: After Judith tells Carol that her hair got really long Tara notices Lydia, and when it cuts to the shot facing Carol and Ezekiel, the white nylon T-marker is visible on the ground, between Lydia's feet. (00:08:25)
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.