The Ghost of General Lee - S2-E6
Revealing mistake: When you see Bo and Luke running around "naked", when they go to that girl's house to ask for clothes, while they are leaving you can see a little bit of the blue jeans that Bo was wearing to bring the naked effect to life.
Days of Shine and Roses - S2-E1
Revealing mistake: When watching the film in the beginning, one of the cops pursuing Jessie and Boss rolls over. As he does so, you can see the roll bars in the car, which accounts for the car not crushing.
Days of Shine and Roses - S2-E1
Revealing mistake: When "Spike" goes to pull the front fender of the car off, you can see the square outline of the spot meant for the spike.
Days of Shine and Roses - S2-E1
Revealing mistake: As Sheriff "Spike" Loomis goes to put the railroad spike into the car's door, there is a square outline of the spot set up for him to put the spike.
Gold Fever - S2-E2
Revealing mistake: Toward the beginning, when the Dukes meet the Texans, when the Texans toss up shot glasses to shoot, you see a white wire attached to one of them, probably to bust the glass on cue.
Answer: Various reasons, but mainly to drive the Dukes out of Hazzard County because the family have been foiling his schemes since his and Uncle Jesse's bootlegging days.
Captain Defenestrator