The Waltons celebrate their parents' 40th anniversary, but the original series started out c. 1933, with children born before 1929.
The timing does not work. It's 1969. The series begins during the Depression of the 1930s, and John-Boy is already around 18. He fights in WWII, so in 1969, he should be around 48-50 years old. But he and the siblings are presented as much younger than they should be. John-Boy is newly married and about to become a father. And the parents should be married much longer than 40 years.
John tells John-Boy a story about how nervous he was before John-Boy was born. He says that Grandpa threw him in the lake to calm him down and the next day John-Boy was born. This contradicts what was said multiple times earlier in the series that John-Boy was born while John Sr. was away fighting in World War I.
When Mary-Ellen starts to check Janet's blood pressure, she puts her stethoscope to her ears before she fits the pressure cuff. In the next shot, Mary-Ellen again fits the stethoscope.
Multiple times the spelling competition is called the 'All County Spelling Bee,' but the sign on the stage says 'All District School Spelling Bee.'
Mary Ellen's daughter Katie appears to be about two years older and her son Clay appears to be a few years younger than they appeared in the first reunion movie which took place in 1963.
When John boy sees Verdie walking down the street , he calls out a greeting to her , referring to her as Mrs Grant instead of Mrs Foster .
During the series, the tree house was always near the barn to the right of the house if you were looking at it. When John Boy hears Elizabeth crying, he goes up to the tree house to comfort her, and it has moved to almost directly in front of the house, slightly to the left.
The movie takes place in the late 1960s, but everyone is wearing modern-style clothing.
When Jeannie is talking to the waitress, she puts her money down on the table twice.
Mary Ellen removes the stethoscope from her ears at least 3 times after checking Janet's blood pressure .
Olivia removes her hand from Elizabeth's shoulder twice .
Janet is not the one who makes the reference to Mary Ellen first becoming a nurse, having 3 children, then becoming a doctor; it was Aurora.
John-Boy comments on TV about the first moon landing during Easter of 1969, but the moon landing happened a few months later, in July.