The phone (which is definitely not in Rockford's trailer) from which Echo Seven dials is the same as Rockford's phone number.
A later scene shows Stacey the missing stenographer in a motel just after midnight. The 70s computer-like text overlay indicates the scene happening at 2405 HRS on 12 Jan. In a 24 hr clock there is no time after 2400. It should have been shown as 0005
When Donnegan and Echo Seven are on the rooftop watching the transfer of the guns onto the boat, the view through their binoculars is at ground level instead of at the rooftop's elevation.
At 18:46 Rockford picks up a timecard for a typist in the federal office. Freeze the frame and you can clearly see the time card is for a movie studio worker. It includes such categories as "report to other studios" and "ext-nite shooting".
The police are pulling Rockford and Bernie over, in the background there's oil/gas refinery tanks. Then the next scene has no tanks, but the freeway traffic.