Other mistake: The premise of the first episode is flawed; "a single choice" should make the difference, the choice being identified as Ms. Carter not leaving the room to get in the observation booth. But in the normal timeline the booth is exactly where all the other characters were. In this reality everyone else is downstairs, with the German spy that inexplicably sets the bomb early. If anything, it's his bizarre, suicidal choice that matters.
Plot hole: At the end of the previous episode, the Watcher gets surprised (literally saying "wait, what?") by the arrival of Infinity Ultron inside Party Thor's universe.In this episode we find out the story of Ultron.Ultron realises for the first time that there are other universes to conquer right then because he can'hear' the Watcher talk (to whom?) and goes after him.So the two episodes don't match;Ultron couldn't have reached the other universe "before" his realization, and Uatu is again surprised by it.
Other mistake: Supposedly the one difference between this universe and the movie canon is that Janet was infected by a zombie virus before she was saved by Hank and Scott. However, in the original movie Janet actively led them to her by 'possessing' Scott and while intelligent, these Marvel zombies can't communicate. Also, Vision is settled in Camp Leigh, which appears to be in perfect shape despite being hit by a missile powerful enough to penetrate in the bunker in Winter Soldier.
Plot hole: The episode has wonderful writing from a pure storytelling perspective, however it has zero coherence with the MCU it is supposedly part of. The show was written way before "Loki", for instance, and concepts like "Absolute points" are at odds with it. Likewise, Strange and the Ancient One's powers are radically different (Strange can't foresee the future but can go back at will without rewinding and his mentor can seemingly see past her own death).
Plot hole: Ultron cuts through Thanos like butter and acquires the Infinity Stones. He does so after he kills all life on the planet (-2). So Thanos has all the Stones (except Vision/Ultron's) years earlier than normal continuity, for no reason. Not just that; Ultron proceeds then to 'silence' the rest of the universe one planet at a time (which would take forever; Thanos wanted the gems exactly to avoid doing that and make genocide efficient). Amongst those planets, one where he fights The Guardians of the Galaxy, including...Gamora, who should be dead or Thanos could have never got the Soul gem.
Other mistake: Ultron exterminates the world population quite literally nuking the planet. Black Widow and Hawkeye survive because they are in the air during the global inferno (that's not really how it works) and for the rest of the episode they saunter about on a world full of the deadliest level of radiation in a nuclear winter (electricity and cellular phones work, too).
Other mistake: Dialogue when the heroes locate the base; "The beacon's location was corrupted in transit, we have no idea where it came from." "Well, it looks to me your message is in non-linear hexacode" "That location looks familiar, Agent Carter?" And Sharon instantly identifies it. It may make sense when you write it, but not when there's no pause between sentences and no 'location' is shown. From "We have no idea where it comes from" to "Does it *look* familiar?" through a non-sequitur. (00:08:00)