Driving their car, when the family arrives at the place of the accident with the Sheep transport truck, Matthew - the one driving - is distracted. Laura just waking up yells out for Matthew to stop. They come to a full stop less than 7 inch (18 cm) from a car standing still in front of them, only just avoiding hitting it. The family gets out of the car and Matthew is seen to have plenty of space to walk between the two cars. Neither of the two cars can be seen moving, and there is simply no time in the storyline for either of them to have moved.
Right after moving to the house in the Shenandoah Valley, the step mom plays a single record on the record player - The Beatles' "In My Life." Although it appeared on "Rubber Soul," it was never released as a 45 rpm.
Any dog that worked sheep as poorly as Lassie does in the opening scene, would have been shot on every sheep property I've ever worked on.
When the Turner family goes to the county fair, they take Lassie too. It would be highly unlikely that you would see a dog roaming around a fair without being on leash. Normally, you are not allowed to bring the family dog unless you are showing the dog in competition.
In the scene when the family is in the car leaving the Collins Store after arriving in Franklin Falls, the father says "Matt, all aboard" but you can clearly see his mouth doesn't move.
In the first scene with the wolf, where it appears inside the den, you can see a stick used by Clint Rowe to agitate the wolf to growl.
A wolf is shown in the movie that takes place in Virginia. Wolves are not found in Virginia or West Virginia. Former wolf dens in both American states are modernly inhabited by coyotes.
When the Turners move into the Collins house, Matt is seeing throwing a ball for Lassie to go and retrieve. One time Matt throws it into the bedroom closet by mistake. Lassie, having never been in the house before would not be able to suddenly find Matt's mothers old diary on the shelf in the closet. Nor would Lassie know where Anne and Steve had carved their initials in a tree after having led Matt to it.