Early on, when Donny throws the fishing catch onto the dry dock, the fish land exactly on a wet spot, obviously left there from a previous take.
After the plane crash, Donny is collecting items around the site. In one scene
the arm of his shirt sleeve is torn - in the next scene it is not torn.
When Julie calls Nora on a pay phone, she simply asks for long distance even though she's calling from Canada to the US (an international call). She also never puts any extra money in the phone box.
In Canada a department of transport employee wouldn't pronounce Z (zee) In Canada Z is pronounced (zed)
When Janet picks flowers, they give zero resistance to her pull and all come out with neatly clipped stems. It's very obvious that the flowers were pre-cut and inserted in the ground material by prop gaffers.
During several scenes, when Janet is crying or whining, her voice is dubbed and it is apparent that the audio is not coming from the actress herself.
The young girl who is lost is named Janet, and her brother calls her Janet many times right after the plane crash. However when her father played by Howard Keel hears her screaming in the forest he starts yelling "Julie, Julie!" As he runs to find the children.