Other mistake: When John Canfield's talking to Floyd, Andy, and the other men they're in front of the display window, which doesn't have any panes of glass.
The Education of Ernest T. Bass - S5-E4
Other mistake: After Ernest T. breaks Helen's window Andy shows up, and there's black tape adhered to the chrome trim at the side of the windshield and also the chrome trim beside the vent window.
Other mistake: When the escaped convict takes Barney hostage, they walk away from the lake and Barney drops the piece of paper with the convict's picture. Later, when Andy walks across the grass he finds Barney's cap and the paper lying on the grass, but the problem is that Andy needs to pull up at the center of the paper because it's pinned to ground, presumably so it wouldn't move or blow away for the shot.
Other mistake: The new game/hobby boxes that Barney hands out to the Gordon brothers have their brand names partially covered. Mr. Potato Head has 'Head' covered, the brand name of the leathercraft set is covered, and part of the name on the metalcraft tapping set is covered.
Other mistake: When Barney and Andy find the trailer that Malloy's hiding in with his partner and Horton (who's tied up), the other trailer that Andy and Barney are standing behind has license plate "DC 269," the same as some other vehicles in previous episodes.
Other mistake: The radio communications consoles on the side desk in the courthouse have a few pieces of black tape covering their brand name (though we know it's Motorola from the visible "M" logo).
The Farmer Takes a Wife - S2-E13
Other mistake: At the end, when Joe Waters parks his car in the sheriff's parking spot his car's license plate number is "DC 269," which has been seen in earlier episodes on other vehicles.
Deputy Otis - S2-E31
Other mistake: Upon arriving at the courthouse, Andy and Barney discover they don't have their keys to get in so Andy decides to go knock on the window at Otis' cell, which he does to wake Otis. However, Otis' cell does not have a window, only the adjoining cell does. (00:20:00)
Suggested correction: Otis' cell does have a window. In the previous episode with Barney's cousin, Barney's pulls the window out of the wall to get Otis out. Also in another episode Barney gets an intercom and places one part by the window to demonstrate how it would work.
It has a window but no glass. It shows Andy knocking on the window to wake Otis up but then it shows him hanging on the bars.
Other mistake: Floyd's car has the license plate number "RD 757" which has been seen on other vehicles in previous episodes.
Floyd, the Gay Deceiver - S3-E9
Other mistake: In the final scene near the end of the episode Floyd calls Andy "Andy Griffith". It's muffled, but if you listen closely it's audible.
Other mistake: When Barney is ready to pour the plaster cast into the shoe prints, there are only a few prints on the ground. There should be a continuous set of prints from the barn door to wherever.