When Hershel and Milton are seated and talking outside the barn (while Rick and The Governor are inside trying to strike a deal), you can see a hearing aid in one close up shot of Hershel. You don't see the hearing aid again.
Glenn is shown cutting a metal grid with a household propane torch. This type of torch does not get hot enough to cut metal in the manner shown - an acetylene and oxygen torch would be required to do that.
When Milton asks to see Hershels leg, he says it's too see how far from the bite it was amputated, but the bite is on the part that was amputated.
When Andrea appears to open the sliding door of the feed store you can see the shadow of the stagehand who actually opened it through the holes in the door.