Plot hole: R.J. Fletcher is shown as a ruthless businessman who knows everything there is to know about Channel 62 - who owns it, how much it's worth, who is running it, the financial troubles it is having and so on and so on. He is also fully aware of the telethon and the fact that George is selling the station as a going concern for a total of $75,000.00. It is simply asking too much of audience credulity or 'suspension of belief' to think that such a hard-headed businessman would not work out that he could, using stooges, buy a controlling interest in the station for $37,501.00, saving himself a small fortune and closing the station down over the objections of his minority shareholders. Something this blatant could not possibly be a character mistake - he is already planning on buying the station for the full price (from Big Louis) so don't tell me he wouldn't just switch plans and buy it from George instead!
Plot hole: If Old Biff changed his past and went back to 2015, he goes back to HIS future, not the bad future, but Doc later tells Marty that if he were to go to the future to stop Biff from taking the almanac, he'd go to the bad future, so Old Biff technically shouldn't have been able to return to "his" future at all.
Plot hole: David Sutton claims he's never read an autopsy report before yet earlier he said he moved to his new town to get away from all the murders he investigated, a job that would have required him to read autopsy reports.
Plot hole: If the Devil made Claire blind again, how did she read the fine print of the devils contract with Toxie saying that there was an escape pod?
Plot hole: According to the detective at the end Walter believes Ray kidnapped his dog, assuming he saw the note that Ray put in Walter's mail slot. But if that note was grabbed along with Walter's mail and the wig it would have burned up along with everything else when the house exploded. So how did Walter know that Ray had his dog?
Plot hole: It seems that after committing 6-odd counts of aiding and abetting, literally right in front of the strict Police Captain father of one of them, Ted and for that matter Bill, would be lucky to only go to military school, regardless of passing or failing one particular class.
Suggested correction: The threat of Ted having to go to the military academy in Alaska was because he was going to fail. Since they passed and graduated, there's no need to attend the military academy. Some time passes before Rufus brings the babes to Bill and Ted, so we don't know what punishment they were given.
This isn't ordinary misbehavior, it is a felony, what do you think the punishment would be? No TV for a week?
I don't have to speculate what their punishment would be. Certainly neither would be sent to military school (which is a TV and movie trope that wayward children get sent there anyways). Your mistake entry is not a plot hole plain and simple.
Plot hole: The Ghostbusters go underground to search for the slime using a map. Even excusing their initial dumb decision to try to dig a hole in the middle of Manhattan when they could have taken that route to begin with, there's no excuse why after their acquittal they never went looking for that river of slime until Vigo burns their lab; they spent weeks studying small samples of the thing but never tried to reach again the source of the infestation to monitor it, which is absurd. (01:00:00)
Suggested correction: The Ghostbusters know from Ray's initial journey down the hole that the river of slime is in the old pneumatic transit system. They are busy re-opening their business and will eventually go back to the river, but that mission gained more urgency once they linked the river to Vigo. Also, they know that the river has been there for years if not decades, and therefore realise that returning to explore it can wait a few weeks.
Plot hole: When cousin Eddie kidnaps Mr. Shirley, Shirley's wife immediately calls the police. She describes Eddie as 'brutish and huge' or something similar, and wearing a 'blue leisure suit'. She also mentions that she got the license plate number of the vehicle. But how did the SWAT Team know to go to the Griswold's house to find Mr. Shirley? Eddie's RV is not registered in the Griswold's name so the plate numbers would not be much help in finding the culprit.
Plot hole: The odd couple tails the suspicious guy bossing around the car company mogul and run a check on the license plate. The response is "Car registered H.W. Scully. No known residence, only address PO Box 25047 Detroit." They tail him a bit, end up in the bowling alley and lose him in the commotion. After that, Leno asks his buddy at the district if he has "anything on that guy Scully", and the answer is "This guy has done anything but rape Bambi. Several weapons charges, assault and battery, he beat a murder rap in Sarasota" etc. And of course, an address. (00:56:35 - 01:01:35)
Suggested correction: The effects of the past being altered may not have happened immediately. It is possible that it took time for the timelines to adjust to the changes of events, meaning enough time would have passed to change 1985 when they return, but not enough time could have passed to change 2015. By the time Doc says if they went back to 2015 they would be going to an alternate future, some time has passed, so the effects of the past being altered and taking ahold in 2015 and altering it are more likely to have occurred by then.
Casual Person
Here is what you say: "perhaps it took time for the time lines to adjust." What kind of time would timelines take? Time is time, it doesn't take time to change the timeline. That doesn't make any sense. Some people claim it was the DeLorean itself that came back to its own original timeline and only then reset itself in the new one, but then the new timelines being erased later on wouldn't have happened either. So its a genuine plot hole.
lionhead
It's established in the first film that it takes time for the changes to take effect. Marty and his siblings slowly disappear from the photo, rather than instantly. Although the scene in BTTF2 was deleted, it was filmed showing Biff dying and slowly fading away after his return to his present.
Yet they were restored instantly without any outside influence at the end of the movie. There are a lot of things wrong with this movie and the first one. Old Biff disappearing should mean that Marty and Doc should slowely disappear as well, even the DeLorean. But they didn't, that doesn't make any sense. The point is there is a plot hole, somewhere. To know where all you can do is look at it logically and then you automatically come up with Old Biff going back to the future but not the alternate future. If he did there wouldn't have been a movie, but that's the plot hole.
lionhead
The timeline didn't change until he made his first bet which was some years I think after receiving it. He immediately travelled forward after giving the act, meaning he will still jump forward to the original future.
The timelines would instantly change, and Old Biff couldn't possibly have returned to "normal" 2015. It's just a poorly-thought-out time travel plot hole (or a deliberate error to expedite the storyline).
Charles Austin Miller
Suggested correction: In context, Doc was saying that they couldn't return to 2015 to stop Biff from stealing the time machine, because Biff didn't steal the time machine in the alternate 2015, he only stole it in the original 2015. Marty and Doc didn't stay long enough in 2015 after Biff returned, and that's why they didn't see any differences. Also, though they were unaware of it, Biff was dead in the alternate 2015, so the disasters he caused might have reverted back after his death.