Corrected entry: When Marty confronts Biff in 2015 and asks when, where, and how he got the sports almanac, Biff retrieves it from a safe and a lock box and carefully shows it to Marty. Because the almanac contained results from sporting events through the end of the century (the year 2000), it would have been rendered worthless 15 years before and would therefore no longer need to be kept in a safe, if even at all.
Corrected entry: When Marty was standing outside the giant TV and the announcement was made about the Chicago Cubs winning over Miami, Marty said he put his money on Miami. He had only been in 2015 for a short time, and before that he was in 1985. There is no way he could have bet on anything in 2015.
Corrected entry: In the year 2015, Marty's daughter Marlene is telling Lorraine that the reason the scenery channel isn't working is because the scene screen repairman called Marty a chicken and Marty threw him out of the house. Why would the repairman call Marty a chicken? Nothing at all makes sense about this, what could possibly provoke a repairman to call the owner of the home he was working in a chicken ? Even if Marty was rude to him, it would make more sense to just call him a jerk, not a chicken. Calling him a chicken likely means he was goading him into a fight and there is no logical reason for some repairman to want to pick a fight with someone he is servicing.
Corrected entry: When Doc opens his case full of currency, it's sorted by decades, and Doc explains that it's purpose is to be ready for all monetary situations. He pulls some currency from the stack labeled 1950's and tells Marty to use it to buy some clothes. However, since the year they are in is 1955, there's a chance that he may be giving Marty money dated anywhere from 1956-1959. Wouldn't it have made more sense to take the currency from the stack labeled 1940's instead, thereby not running the risk of drawing attention to themselves with money printed with 'future' dates?
Corrected entry: Marty sees himself talking to his parents one last time before his other self goes to meet Doc at the clock tower. At this point Biff steps up to Marty and comments on his disguise. The problem here is that in the first movie Biff is never seen again after George punches him. If he had woken up he would have been there to confront the first Marty at the door after telling his parents about the burned carpet, or even George for hitting him. So what happened to Biff the first time if he wasn't there when '55 Marty walked out the door?
Corrected entry: After Doc and Marty leave the cafe 80's to get Jennifer back from her 2015 house, you see old Biff retrieve the sports almanac from the trash can, he then audibly says "so Doc Brown invented a time machine!" Next scene in the DeLorean, Doc says he thought he saw something in his rear display, a shot of a yellow cab is then displayed. No way for old to Biff get a cab and catch up so fast, as the DeLorean had been parked in an alleyway, with no cab in sight.
Corrected entry: In the scene in 2015 where the future Lorraine and George McFly come to eat dinner at Marty and Jennifer's house, Lorraine cooks a pizza in a toaster oven. After cooking for 3-4 seconds, Lorraine removes the pizza, which is sizzling hot. However, Lorraine removes the hot pizza with her bare hands without burning herself.
Corrected entry: You'll need slow-mo and pause for this one. When Griff's three mates throw down their hover boards they actually throw them beyond the camera, then digital super-imposed ones land in front of them. Watch closely at the girl's board (on the right) it's transparent, then the guy in the middle jumps beyond the camera and again super-imposed legs land on the hover board. (00:18:00)
Corrected entry: After Marty talks to his parents after playing on stage he casually strolls out the door just opening the door a fraction, but in Back to the Future 2 he knocks his other self unconscious by flinging the door open. That shot was seemingly done again for the second movie so Marty could be knocked unconscious. (01:28:47)
Corrected entry: We see that George McFly died in 1973 when Marty checks the newspaper; the article on the front page says he was murdered, with a sub headline that reads "Local Author Dies." However as we saw in the original Back to the Future, George didn't get his first book until 1985 when Marty came back from 1955. Therefore George was not an author in 1973 when he was murdered. Even if in the alternate future George wrote earlier, when Doc and Marty fixed the future the newspaper should not say "Local Author Honored" because in the non-alternate future he was not an author until 1985.
Corrected entry: When Marty's son walks by young Jennifer in the hallway of his home, he thinks is the older Jennifer and says "Hi mom, nice pants". Later at dinner, Marty Sr. and Lorraine are talking about how Jennifer is late coming home. Marty Jr. is sitting right there and doesn't even mention how he just saw his mom in the hallway.
Corrected entry: When Marty buys the sports almanac, how does he get the money to do it? Considering a Pepsi costs 50 bucks, the almanac probably costs several hundred dollars. How many teens from the 1980's just happened to have that amount of money in their wallet at any given moment? He didn't get the money from Doc since Doc didn't even know he bought it until after the fact.
Corrected entry: When Biff and his gang crash through the windows of the clock tower with their hover boards, Marty goes to give his back to the little girl, but she says "keep it, I've got a pitball now" and shows him Biff's hover board. Only problem is it's still in the clock tower wreckage, attached to the other 3.
Corrected entry: The cooling vents on the back of the DeLorean change between silver and black throughout the film. A clear example of this is the first landing scene of the DeLorean in the alley in 2015.