Corrected entry: When Marty escapes the Libyans at the Twin Pines Mall, hits 88mph and ends up in Old Man Peabody's barn, driving in through a large opening in the barn before crashing. However, the cut to the inside of the barn shows no form of entry other than the closed doors the family are entering. In addition the inside of the barn is very small compared to the outside view. (00:30:10 - 00:31:55)
Corrected entry: On the DVD version, in the scene where Doc gets shot and then later reveals to Marty that he was wearing a bullet proof vest. A vest does not work in the way shown in the movie. It doesn't repel bullets (as shown in the "impact points" in the vest he displays), it absorbs them. Read how a vest works from howstuffworks dot com and you'll see what I mean. In addition, it looks like he is wearing only a Threat Level 2a class vest. An AK47 or similar weapon with a 7.62mm round would go clean through the vest, through Doc, and out the other side thus killing him and ending the story. The only style of vest that can withstand that sort of impact is a Threat Level 3 class vest (the style that specialized units in the military wear). This style is very bulky and is extremely difficult to conceal like Doc did. In addition, it has a ceramic plate in it which would have shattered upon the first impact and failed to protect against multiple impacts from that kind of weapon, and definitely not show "impact points" of twisted metal.
Corrected entry: The DeLorean has 'Good Year' tyres - this is a deliberate mistake to create an in joke, as the brand is actually 'Goodyear'.
Corrected entry: When Marty travels back to 1955 the DeLorean first strikes a scarecrow, then drives at high speed into a barn and finally crashes through the barn door to escape. Later, when it returns to 1985, it crashes into a movie theatre front before it can stop. After all this mayhem the DeLorean doesn't have as much as a scratch on its nose.
Corrected entry: After Marty returns to 1985, he discovers that he now has the new Toyota truck he wanted, while the rest of his family is forced to share one car. Why would Marty, the youngest of the siblings, who is still in high school, have his own brand new truck while his older siblings and both parents have to share one other vehicle?
Corrected entry: After Marty reunites his parents, he and his siblings all reappear in the photo and all is well. However, in order for Marty and his brother and sister to exist again, it would mean that Marty's parents would have to have sex at the exact same moment all three times to conceive them. Even if they were a few seconds off, it wouldn't be the exact same three kids. Similar maybe, but not exact. Now that George is more successful, he will be doing many things differently in his life so the chances of him and Lorraine having sex at the exact same millisecond all three times to have those exact three kids is beyond astronomical.
Corrected entry: When Marty is trying to prove to Doc that he is from the future, he shows him his driver's license and the photo of himself and his siblings. Doc immediately dismisses them both. Doesn't Doc notice that the quality of the color in the photos is much better than any color film that existed in the 1950's? Wouldn't that grab his attention?
Corrected entry: If everything that happens in the past, determines what happens in the future,and there in between, then wouldn't it make more sense for the picture of the family, when it starts to come back, to have them dressed differently? Such is the case when they are in the new family scene, when they come back.
Corrected entry: When Marty shows Doc the flyer from 1985 about saving the clock tower, this gives them the time that the clock will be struck by lightning, 10:04pm on that coming Saturday (11/12/55). However, the main problem here is that the time is only given in hours and minutes, and since lightning moves at the speed of light, an entire lightning strike lasts only fractions of a second. Doc and Marty have no clue as to what second the lightning will strike during that minute, and it isn't given a thought. In reality this would cause a tremendous dilemma if the Delorean had to pass at a precise second. And since the clock on the tower lacked a second hand, they would need a sychronized watch to determine the second the strike occurs, even if they knew it. In the movie it is assumed the strike occurs at 10:04:00, which is fine, but for more realism they could've added a second hand to the clock to eliminate this plot hole. It would have been stuck in place as the other hands after the lightning strike.
Corrected entry: At the very end, Marty tells Doc that he'll have to back up as they don't have enough roads to get up to 88mph. The next shot we see shows the avenue stretching off at least a mile into the distance, with plenty of road to reach that speed. Since the DeLorean was able to achieve 88mph in a parking lot, it should be fairly obvious to Marty that there is no issue with them not having enough road.
Corrected entry: When Marty pulls out of the barn and runs over the pine tree, it's pitch black outside (the sun hasn't risen yet). The subsequent shot shows Marty driving his car and telling himself it's just a dream...now it's complete daylight. Is the Twin Pines Mall/Twin Pines Ranch so far away from Hill Valley that it takes a sunrise's-worth of time to DRIVE from one to the other? Doubtful, since it only took Marty about 15 minutes to skateboard there from his house (and pick up Doc's camcorder along the way).
Corrected entry: American police may be so lackadaisical that they don't attend the scene of a car racing noisily around a car park, followed by a loud crash of a van hitting a shed, but I find it hard to believe that they don't investigate continuous machine gun fire from the same area. There are occupied building all around the car park, and there is plenty of time for them to turn up.
Corrected entry: When Marty is being chased by the terrorists, he disappears through time, and the terrorists crash their van into the photo-booth, which presumably stops them dead in their tracks. But really, how would trashing that small booth make the bad guys irrelevant from that point onward? They weren't killed. So realistically they'd all get out of their crashed van and proceed to wreak more havoc. Yet in the time it takes Marty & Doc Brown to gather up all their stuff and drive away in Doc's van, the terrorists don't lift a finger to chastise them or confiscate the remaining plutonium.
Corrected entry: When back in 1985 Marty's mom asks if this is the night for the big date, Marty answers "How can I go to the lake when the car is wrecked?" His family reacts by going out and checking George's BMW. Seconds later we see that Marty has his own truck - shouldn't they have been checking on that instead? And if it's because he talks about the car (i.e. the BMW) instead of the truck, they should have wondered why he was going to take his fathers BMW up to the lake instead of his truck.