These three bloopers all fall into the category of visible equipment, ie. equipment that should be out of sight. In 'Gold Fever' this car flips during the chase scene with Dr. Homer Willis's RV. The explosion blows away the foliage that was covering the pipe ramp, leaving it exposed. In 'Duke vs. Duke' Flash raises her ears when Rosco tries to jump to victory at the end of the race. It doesn't come out too well in this screengrab, but if you watch the scene you can clearly see that there's a thin black wire pulling the ears up (I've arrowed the visible one on the left ear). In 'Ding, Dong, the Boss Is Dead' the Dukes have to stop Boss's runaway coffin. The coffin then sails through the air and ends up in a tree/bush. In the long shot there is no tree/bush anywhere near the spot where the General blocks the coffin's path. Additionally, the coffin follows an arced trajectory due to the fact that it's swinging on a very obvious cable.