As Oscar gives John Boy a lift, early in the journey the rear projection is revealed as the camera frame misses the rear projection screen, leaving the edge of the screen black, with part of the cars window in front of this space. The mistake appears to be spotted as the camera then pans left slightly to realign with the rear projection image.
While the Waltons are at the carnival at around 30:20 inside the game tent, a pinball machine is shown with flipper buttons on the side of the machine. Humpty Dumpty was the very 1st pinball machine that had flippers and wasn't released until 1947.
The livestock building seen in the county fair scenes is obviously Ike Godsey's store with the sign changed.
Olivia takes the same cake out of the pan twice .