Another Mother - September 30, 1981 - S2-E13
Plot hole: Sam wallops both kidnappers and rescues the son. They then leave the two child molesters unconscious beside their van. No one calls the police or has them arrested, so they're free to kidnap another kid. Sam doesn't leap until after an epilogue in which the loose ends are supposed to be resolved - but this question is left unanswered. It's not excused by a "just because we didn't see it happen doesn't mean it didn't" defense. The viewers shouldn't be left with a dangling plot hole, and one line could have cured this one.
Desertion of the Dinobots (1) - S2-E19
Plot hole: Perceptor discovers that the reason for their malfunctioning is because their Cybertonium has deteriorated after millions of years of being exposed to Earth's atmosphere. The key word here being 'millions'. This explains why the original Transformers who crash landed on Earth (4 million years ago) are affected, but newer characters like Perceptor, Powerglide, Hoist, etc. are affected despite the fact that they have only been on Earth recently.
Plot hole: "Showdown": Darien's lost hat and jacket reappear without explanation after Kane finds him wandering in the desert. Also unexplained is how Kane conveniently happens to be leading an extra, unnecessary horse - unnecessary, at least, until he stumbles across the stranded Darien. (00:15:00)
Forever Red - S1-E34
Plot hole: Tommy states that he and the other Zeo Rangers destroyed the Machine Empire's leaders and ultimately destroyed the Machine Empire except for the Generals who escaped. This is not true - Lord Zedd and Rita destroyed the Machine Empire leaders at the end of series 4, and the Space Rangers destroyed them again in Countdown to Destruction in series 6. The Zeo Rangers never destroyed the Machine Empire.
Suggested correction: How would Tommy know that? He didn't watch the show or know the ins and outs of what happened in space. This is what he believed based on his experiences on Earth. Everything you described is factually correct, but Tommy did not witness this. So, to his knowledge, he destroyed the Machine Empire.
Plot hole: In the bait and switch section, why does anyone involved agree to Leland being Ben's attorney when both victims are relatives of Leland? Neither Ben nor any of the police are in on Cooper's plan, and it seems implausible at best that they would agree to this.
Sins of the Fathers Chapter 6: Framed - S3-E6
Plot hole: After Peter Parker is framed and arrested for selling government secrets to foreign organizations, he escapes police custody and goes home to retrieve his Spider-Man costume that was simply hanging in his dark room. If he was arrested for selling government secrets then surely the police would have searched his home and found his costume (as well as equipment) in the process. Since the police car was visible in front of his house, it seems very strange that police didn't search his home.
Plot hole: When Lawquane spots the droids in the field, he identifies them instantly as commando droids. But as he had left the Republic Army shortly after the first battle on Geonosis (the one which started the war) and has lived as a farmer ever since, and since the commando droids are relatively new (see "Rookies"), how can he know what they are? With his lack of battlefield experience, he should simply call them battle droids.
Plot hole: Gaeta and Tigh both reference the fact that the Galactica crew computes the changes in stellar drift for FTL jumps and then sends out the info to the rest of the fleet for their use. However, when they fail to rendezvous with the fleet after the emergency jump, Gaeta realizes a mistake has been made and says that Galactica's info is out of date. This creates a major plot hole because if Galactica sends out the new info to the fleet, Galactica would always have the most up to date info for FTL jumps. The crew would be able to solve the lost fleet crisis by simply reloading the last coordinates that Galactica sent out and jumping there where the fleet would be waiting for them. There would be no need to go back to the previous coordinates and recompute the jump.
Plot hole: In 'Oasis,' several times in the episode, specifically when they took Trip captive, the holograms appeared out of nowhere brandishing weapons. The holograms can walk through walls, which we saw, but the guns were real. We saw them hit the deck when Liana deactivated the holograms. So how did they appear with the guns? (00:34:00)
Plot hole: When John inserts Cameron's CPU, she restarts nearly instantly. She recognizes John right away and speaks to him by name. Yet seconds later, we see through her eyes as her system reports recognizing him, but she already does.
Plot hole: Series 2, Episode 11, The Agenda (1). The Tripredacus Council explains that Ravage will be able to find Megatron and the others by tracing the transwarp wavefront back through time to its source. If he truly did follow it back to when it started he would have arrived moments after Optimus destroyed the alien weapon in "Other Voices: Part Two" which created it, yet he arrives considerably farther in the future.
Plot hole: When Mr. Ballentine is telling Emily about her assignment, he sets the blue folder down near his side of the desk before he gets up. Then we see Emily pull it across the table and quickly peek in it. When Ballentine turns around, the folder is still close to Emily, which shows that she at least tried to look in it, yet Ballentine says nothing about it no longer being in the spot where he set it down. If Emily thought that it was okay for her to look in the folder, she wouldn't have waited for Ballentine to turn around before she touched it.
Plot hole: Michael uses herself as bait to trap her future self, putting her own life in jeopardy with the reasoning that her future self will come back to save her. All well and good, except they have a backup plan with the doctor to resuscitate her if needed, meaning her life isn't really at risk, or nowhere near as much as might be implied. And her future self would undoubtedly know that, having lived through it in the past, so not swoop in to save her. Or even if she did come, would also know it was a trap.
Suggested correction: ***SPOILER ALERT*** But, as it turns out, The Red Angel that comes to save her is NOT Michael, but her mother, who would not necessarily have known about the backup plan.
***SPOILER ALERT*** That it was her mother doesn't stop it being a plot hole since they thought The Red Angel was future Michael, and future Michael would know that present Michael wasn't really in danger so they weren't presenting a situation, _according to what they believed_, that required future Michael to act. It being the mother was a plot twist that created a motivation to act that the present people had no reason to think would exist. Basically, unless they presume a split timeline (i.e. this present is a different past than The Red Angel lived through), making a trap for future Michael that present Michael is involved in makes no logical sense.
Alternatively, Michael would have to come back, KNOWING it was a trap, to prevent the timeline unravelling.
The point of the exercise is they were setting a trap. If it didn't work, then Michael wouldn't have to come back to "prevent the timeline unravelling (sic)", even if that were a thing - it presupposes a fixed, unalterable timeline, which goes against their attempt to send the data to the future to protect it, and thereby alter the future. Even with an unalterable timeline, it would only work if future Michael had chosen to allow herself to be trapped, but in that case why wouldn't future Michael just voluntarily come back to help? Since her being trapped wasn't a certainty, there was no reason to think she would be given that the current Michael, and therefore also future Michael, knows a trap has been set, but one that doesn't actually threaten current Michael. The whole premise of the trap, under their assumption that The Red Angel was future Michael, is completely flawed and made no logical sense.
The fact that The Red Angel was in the future, and that they had a backup plan meant that The Red Angel never should have come back in time, ever. Because the backup plan would be the recorded history, thus, she never would have died. Thus, nothing to save. Face it, everything in Discovery is a plot hole.
Plot hole: The Seaview's crew have a wild shootout aboard ship, and their bullets are seen to go all the way through a 6-inch-thick hatch door. Gee, you'd think that somewhere during their military training, somebody would have taught these guys why firing high velocity weapons on a submerged submarine is a really bad idea. (00:38:15)
Plot hole: (Ep. 5) The weapon Stephen finds in a desert is a H&K G36. He states that it's not a military weapon and is mainly a mercenary weapon. The G36 is used by several police and special forces units in the world, including the British SAS, which could suggest another nation's or British government branch's involvement. Comment was probably made to deepen the intrigue of the season plot.
The Man Who Was Never Born - S1-E6
Plot hole: Andro has memorized "every detail" of Cabot Jr.'s life, including his mother's name, Noel. Yet when he travels to the past, meets Noel and learns her name, he still mistakes Cabot Sr. for Cabot Jr., who isn't born yet. Having memorized all those details, he would have known the moment he met her that Noel was Jr.'s mother. Andro's confusion makes no sense. (00:28:00)
Plot hole: Dr. Adam Soong is initially presented as a discredited scientist, banned from the scientific community; he gets debarred and his funding revoked. And it's not an internal matter; he is publicly exposed for it. His daughter in episode 6 even finds out this information on Google. Several news articles call him "mad scientist" and such. However, this same person at the same time throughout the rest of the season has every bit of pull and influence, not just through undercover channels, but is treated with the utmost honor and deference by the NASA PR people at public events.
Normal Boy/Birth of a Salesman - S1-E3
Plot hole: Throughout the show, many characters state that Jimmy was responsible for the meteor almost destroying Retroville in the episode "Normal Boy", however, how would anyone even know that? The meteor was put on course after being hit by some kitchen objects shot into space by Jimmy's orange juice machine. Neither Jimmy nor his parents or anyone saw the objects go into space, much less witness them causing the meteor head straight to earth, especially since the meteor wasn't detected until the next day.
Plot hole: In Episode 1-7: The Serene Squall, the Enterprise is at the edge of Federation space, and it is stated that it would take two days for a message to be received by Starfleet. Later in the episode, they have no problem establishing a real-time connection to Vulcan, which, according to canon, is only 16.5 light years away from Earth.