In the first Wilderness Family movie, the character Boomer is rather slim, about 180 lbs. Boomer is a mountain man who is constantly on his feet, hiking in the mountains and has a meager, low fat and calorie diet. But in this film, Boomer is over 30 lbs heavier. Considering his lifestyle, this not likely.
The first movie when the Robinson family moves to the mountains it is 1975 and their daughter Jenny is only about 9 years old. This film takes place in 1979, only 4 years later, making Jenny only 12 or 13 years old. But in this movie, Jenny is closer 17 or 18 years old, 5 years older than she should be.