When the English soldiers are welcoming the American POWs to the mess hall, Paul Lazzaro is seen sitting down to eat, but in the next shot, he's standing up putting a safety razor in his jacket pocket.
When the siren sounds, the American-turned Nazi propagandist Howard Campbell goes into the bomb shelter with the rest of the American POWs. But after the bombing is over and the men come out of the shelter, he is nowhere to be seen.
At 26 minutes, when the British POWs come out of the hut singing, the man on the far left is wearing a peaked cap but in subsequent clips he is wearing a forage cap.
At the beginning when Billy Pilgrim is typing in the house, the letter "A" in the word "what's" did not fully get typed onto the paper, but when it shows him typing the next line, the letter "A" is fully inked in without any trace of error correction.
When Billy Pilgrim is asked by the American soldiers, "Where's your rifle?", he replies that he doesn't have one because he's a chaplain's assistant. However, in the United States Army, the primary duty of the chaplain's assistant in a combat zone is to protect the chaplain, so all chaplain's assistants must carry rifles. Because Chaplains are considered ministers in uniform they are forbidden from carrying weapons even when in combat zone.
When Billy is about to get his Electro Shock, the doctor says the bombing of Dresden was actually worse than that of Hiroshima, but Dresden was bombed (six months before Hiroshima) in Feb 1945. Hiroshima was bombed in August 1945, so they couldn't know something that had not yet happened.
The voice tells Billy, Tralfamidor is 423 billion miles from Earth. But Jupiter looms large in the background and which is only 440 million miles from Earth.
An aerial shot of the aeroplane in which Pilgrim is flying is reversed to make it appear to be flying left-right. The registration is reversed as it's actually a shot of the left side of the aircraft.
When Barbara is driving Billy home from the hospital and pulls the car up to his front door, it is already open.
In the scenes of Tralfamadore, the planet Jupiter (easily recognizable by its giant red spot, which is a massive permanent storm) is visible in the background, but it never rotates.
Just after the bombing of Dresden, Young German Guard runs off through the bombed-out ruins. But the rubble is already compacted, and has many walking trails through it.
In the movie clip of Montana Wildhack playing an ancient Greek, she opens her mouth wide revealing metal tooth fillings.