When Kenny rides up on the motorcycle to pick up Mr. Holcomb to take him to the trailer, a large burst of white smoke appears on the left to represent dust, but it shows up before the motorcycle has reached that point.
When Kenny comes up to pick up Bob Halcomb on the motorbike, the shadows change drastically. As Kenny drives up, the shadows are short, like 10 or 11 am. As Bob is getting on the bike, they are long, like 7am. As they drive away, the shadows are short again.
As Kenny is driving the motorbike up the steep hill, Bob looks to his left, over a cliff. But when the scene switches with the camera looking over the cliff, it is to the right of the bike.
When Kenny and Bob arrive at the trailer, there is dirt on his shirt on the shoulders. Rear camera shots of Kenny in the trailer clearly show this. But frontal shots have the dirt disappears.
After being pushed in the water, you can still hear Kenny singing even though he is under the water.
Flying from L. A. (6000 Miles !) Lufthansa has been chosen flying directly to Stockholm. In a Boeing 727. As Flight LH212. Tell me more... LH never flew nor does fly L.A. - Stockholm. The 727 does not have a range of 6000 Miles unless in-flight refueling is applied. And flight LH212 these days is scheduled from Frankfurt to Dresden. But even in 1965 all LH flight to North America did range in the 400s, e.g. 450, 460, 419...
The cars' steering wheels are in left side and are driving on the right while Sweden had traffic on the left until 1967, thus showing that even the Swedish scenes were shot in the U.S.
When Mr. Holcomb & Karin check into the hotel they are given room 104 but later when they are searching for his daughter and stumble into 106, Karin states that this is their room.
When Kenny is playing guitar, both in the beginning in the house and later at the trailer, it is clear he isn't playing the guitar. In fact at the trailer, he doesn't move his fingers, yet the guitar sounds change keys.
All of the boats at the dock have California registrations even though the scene is supposed to be in Sweden.
When Bob arrives at the Stockholm hotel, a boom mic is briefly visible in the car's windshield (twice).