When the royal party is departing Northern Ireland the registration of the plane is G-ALWF. In the next shot showing the plane in the air the registration is G-AMOJ.
Princess Margaret & Peter Townsend are seen riding near Windsor and there is a cutaway to a circling bird of prey. The bird in the film is a Red Kite, which in the 1950s would have not have been seen in England.
When Queen Elizabeth boards her aircraft, a Vickers Viscount, the sound played for its engines is that of a piston engine, whereas the Viscount was powered by turboprops. Later, as she exits the aircraft, red plugs are visible in the engines which are supposed to be removed prior to flight - revealing the aircraft as a static display from a museum.
The Queen is showing sitting down watching TV coverage on the news of her visit to Northern Ireland that day. The actuality is based on newsreels of the day which would not have been available until days later and screened only in cinemas. UK TV news bulletins of the early 50s were limited to read bulletins delivered by an announcer. Pathe did send newsreels to the Palace but usually for special occasions.
When Margaret telephones Elizabeth from Salisbury (Harare), it is night-time. In England, Elizabeth answers in clear daylight. As Harare operates only one hour ahead of British Summer Time, this eventuality would be impossible.