When Miss Eland calls Straker before leaving, she uses the lavender cordless phone. Straker picks up the orange phone. In Identified (1970), she used the green phone as an intercom. He later uses the orange phone again when talking to her about Foster visiting. Later, Alec picks up the green phone on Straker's desk and Miss Eland picks up the lavender one again. Finally, when Starker calls her near the end, he uses the green phone.
When Commander Straker is on the outside film set with Paul Foster he fires the pistol three times, on the third shot we hear a ricochet sound. This cannot possibly happen as later we see that the pistol is loaded with blanks so there is no bullet to ricochet. (Note: Straker explains that he's using an "acoustic gun", which produces artificial sounds, including the ricochet).
When Straker and Foster are walking inside the set, the shadow of a camera can be briefly seen in front of them.
The end credits has the names of Vladek Sheybal (Dr. Jackson) and Paula Li Shiu (Tsi Chan) misspelled.
In addition to the ricochet error with the gun, it is clearly a prop gun as the slide never moves when Straker fires it.
The camera the co-pilot used was 110 format (or smaller), but Foster shows 35mm slides.
Foster uses his right shoulder to push open his apartment door, and then rubs his left shoulder.