When the kids from Shelbyville are dissing the kids from Springfield, Milhouse's backpack changes from blue to purple and then disappears between shots
After Bart attempts to escape by using spray paint cans as rockets, his feet alternate between clean and spray-painted for a few shots.
When Martin interrogates the little boy with the lemonade stand, the child's older brother intervenes. When Martin calls out to Nelson for help, the wide shot reveals that the lemonade stand is on the right side of the screen. In the next shot, it is on the left, on the opposite side of the characters.
Flanders' RV has the entry door on the driver's side (left) when they enter it the first time and when they leave after being towed to the impound lot, all other shots and scenes show the door on the passenger side (right) or no door on the driver's side.
When Ned's RV is taken to the compound, the gate closes left to right (looking into the compound), when they try to leave the compound, the gate also closes left to right. It should close right to left as it's looking out of the compound.