Chapter Four: The Body - S1-E4
Continuity mistake: Right after Nancy puts together the torn photo of Barb at the pool it cuts to Dr. Brennan and crew in hazmat suits. At the beginning of the shot when they try to reach Shepard on the comms, the digital clock reads 6:54:08. After Brennan says "Try him again.", the shot has the clock blurred in the background as 6:40 something, and a bit later it reads 6:40:55. (00:27:20 - 00:27:54)
Chapter Six: The Monster - S1-E6
Continuity mistake: Eleven is in the shop and stealing eggos. As the freezer door shuts she walks away holding three boxes. The next shot of her walking towards the exit she is holding four.
Chapter Five: The Flayed - S3-E5
Factual error: When Eleven is handed M&Ms in the hospital she is given green and red. Red M&Ms were not reintroduced until 1987. (00:42:28)
Chapter Seven: The Massacre at Hawkins Lab - S4-E7
Continuity mistake: Eddie is still wearing a denim vest he took off his body and threw at Steve a few seconds earlier. When the camera cuts away and back, the vest is gone again. (00:15:19)
Chapter Eight: The Battle of Starcourt - S3-E8
Factual error: Because of the way radios work, when Suzie and Dustin are singing their duet they wouldn't be able to hear each other and the rest of the party would only hear a garbled mess. Per frequency only one radio should transmit at each time, so all the others can receive. If multiple radios are transmitting simultaneously, the signals will overlap and result in unintelligible noise. (00:35:53)
Chapter Seven: The Massacre at Hawkins Lab - S4-E7
Other mistake: When Hooper was trying to light the alcohol-soaked rag to make a torch, his lighter wasn't working at first. He finally got a flame at the last minute. However, the sparks alone should have been enough to ignite the flammable rag. (01:00:33 - 01:02:03)
Continuity mistake: Eleven makes the helicopter fall from the sky and blow up some army vehicles. Within a cut, it's much earlier in the day as the sun is right above her. Prior to this, it was lower in the sky and returns that way as she and the rest of the crew are driving away.
Chapter Seven: The Bathtub - S1-E7
Continuity mistake: When Mike and Lucas notice a van pulling out of a side street and coming to them, the sky is blue, but in the next shot, it is orange. (00:04:03)
Chapter Two: Vecna's Curse - S4-E2
Continuity mistake: After Mike kisses El on the forehead, Jonathan is in the back grabbing his glasses from his pocket. In one shot, he's grabbing them out, and then the next shot has them at waist-level.
Chapter Five: The Flayed - S3-E5
Audio problem: When Joyce, Alexi and Hopper go to Murray's, Murray points a double barrel shotgun at them and it makes a sound of a pump action shotgun.
Chapter Six: E Pluribus Unum - S3-E6
Continuity mistake: When the librarian picks up the phone he picks up the one in the middle, in the next shot we see he has the one to the left and when he hangs up it's the one in the center again.
Chapter Five: The Nina Project - S4-E5
Continuity mistake: The seat belt keeps appearing and reappearing on Nancy's shoulder as she's driving.
Other mistake: When Will is in the hospital, talking about being frozen, they cut to the hallway and the lights on the suspended ceiling are 2' x 4' LED lights that didn't come out until the 2000s.
Suggested correction: There is nothing to indicate they are LED lights. They appear to be translucent panels illuminated by fluorescent lights.
Chapter Seven: The Massacre at Hawkins Lab - S4-E7
Plot hole: The upside down should be mirrored, i.e. all left is right and right is left. When the team finds a gateway where Chrissy died, they should be seeing a mirror image through the ceiling. Also, all buildings should have been reversed. Directions to get there on the bike would have been confusing and reversed, and when any writing was seen in the upside down, it would have been backward.