Plot hole: When Indy is stepping on the letters at the end, trying to spell out God's name, he steps on J, incorrectly, causing it to collapse. When he falls through, however, he grabs onto another letter so as not to fall down. The letters he grabs onto and pulls himself up are an L and a Y, which are not in the word Iehova, so should have collapsed too. (01:46:20)
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: Right after the Joker goes into the cathedral with Vicky, Batman follows him with no one else entering in between the two parties. How then did Joker's goons get to the top of the cathedral before Batman or the chopper? They couldn't have planned it since Joker had to tell them where to pick him up, and they didn't know he would chase after Vicky to that particular location.
Plot hole: During Riggs' last fight with Adolph, Adolph holds the knife in his own hand as Riggs forces him to stab himself very slowly. At any point, Adolph could simply have let the knife fall or just tilt down before that happened. Nothing Riggs is doing is making such impossible. "Locking" his wrist does not prevent him from letting go of the knife. It only prevents him flexing his wrist. And this guy is a trained killer, fighting for his life. Better to battle for control of the knife than just let it kill you.
Plot hole: Bond goes after Lupe after she leaves the casino table, and they have quite a lengthy, hush-hush conversation. It's a casino, and there are cameras everywhere. Certainly, this would have been brought to Sanchez's attention since he was already leery of Bond and possibly Lupe.
Plot hole: Granted, Coffee is suffering from "high-pressure nervous syndrome," but if you're a Navy SEAL, wouldn't you notice whether or not your pistol has a magazine in it? Monk pulls the clip out of his jacket and starts knocking rounds out of it for the rig crew's benefit; the same dramatic effect could have been achieved with a handful of cartridges he could let slip through his fingers. You could argue that Monk didn't have enough time to unload the gun and replace the magazine, but in that case, I think the scene where Monk briefly had the gun should have been a bit longer. (Even had the empty magazine been IN the gun, Coffee still might notice the difference in weight, but that would be easier to suspend your disbelief for.) (01:43:53)
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: Megan is suspended because the police were not able to find the gun the robber had (stolen from Eugene at the scene) and believed that she had killed an unarmed man. This is very unrealistic because surely they would have interviewed all of the hostages/witnesses at the robbery and each would have easily confirmed that the robber had a gun, and possibly that Eugene might have been missing right after the incident.
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)
Plot hole: They seem to break a lot of rules in the main event between Mimi Lesseos and Jan Mackenzie's. They brawl outside the ring long enough to be counted out, choke outs on the ropes long enough to be disqualified are some examples.
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.
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.