Chapter Five: The Flayed - S3-E5
Visible crew/equipment: While Bruce chases after Nancy and Jonathan they hide in the OR, then Nancy picks up the red phone and shouts, and in the following closeup of the ceiling mounted domed light, the upside-down reflection of a crew member wearing shorts and sneakers can be seen quickly. A few minutes later, after Jonathan jabs scissors into Tom's throat, when Jonathan leans back out-of-breath there's another closeup of the surgical light, and we can see the upside-down reflection of the cameraman's arm and part of the camera as it moves closer, then it's visible again a few shots later. (00:43:10 - 00:46:40)
Continuity mistake: When Mike and Will are discussing Will's visions near the start of the episode, the sweat stain on the front of Will's shirt disappears and reappears between shots. (00:01:30)
Chapter Seven: The Bathtub - S1-E7
Factual error: High school basket ball courts didn't have a three point line until the 1987-88 season - not in 1983.
Chapter Three: Holly, Jolly - S1-E3
Continuity mistake: When Mrs. Wheeler bursts through the door, angry with Nancy about lying to the police she throws her purse down. When they get to the kitchen she throws the same purse down again.
Chapter One: Suzie, Do You Copy? - S3-E1
Continuity mistake: When Billy crashes his car, it stops and breaks down. He moves to the bonnet and a clear hissing from a damaged is audible. Then all the mess happens and the episode ends with the usual cliffhanger. When the second episode starts, Billy's car battery is still up, even with the headlight turned on, and the car starts at once with no problem whatsoever.
Chapter Four: The Body - S1-E4
Factual error: When Chief Hopper cuts open the fake body of Will, it appears that he opens a knife with a thumb assisted blade which wasn't invented until 1995.
Other mistake: In the beginning when Kali and her gang are running from the police in Pittsburgh and she "collapses" the tunnel, her 008 tattoo is shown this way so we can read it as such, but it should in fact be read 800 to be the correct way. (00:03:15)
Chapter Three: The Pollywog - S2-E3
Factual error: The cordless drill used to fix door bolts in the new cabin is modern, not from the 80s.
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 Five: The Flayed - S3-E5
Continuity mistake: In the woods, when Alexei is running with Hopper chasing after him, the individual shots of each of them running are flipped. Note Alexei's shirt pocket and Hopper's bloody head wound. (00:22:30)
Chapter One: Suzie, Do You Copy? - S3-E1
Continuity mistake: In Bruce's hamburger the salad is on the bottom and the bacon is on the top, in the next shot the salad is on the top and the bacon has disappeared, replaced with ketchup. (00:23:05 - 00:27:10)
Chapter Four: The Sauna Test - S3-E4
Visible crew/equipment: When Mike and his friends are discussing the Mind Flayer needing a new host, El asks how they'd be able to tell if someone is a host. Then it cuts to Hopper and Joyce pulling up in front of Town Hall, and before Hopper gets out of the car the boom mic is reflected on the squad car's window. (00:14:25)
Chapter Seven: The Bite - S3-E7
Continuity mistake: At the very beginning the band the camera pans by is totally different from the one standing behind the mayor later on. For one there are no more clarinet players, a cymbal player suddenly appears right behind where the mayor stands and the drummers are 3 totally different boys, with the 3rd from the right missing his glasses suddenly and the second drummer being much shorter. (00:00:40 - 00:01:15)
Revealing mistake: When Bob and Joyce have lunch, Bob pops open a can of soda (which is period appropriate). The scene cuts to Joyce, then back to Bob. It is clear from how he is holding the can, and how he pretends to drink from it, that his newly opened soda is actually empty.
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)
Factual error: When Hopper's daughter is dying in 1978, the staff says that the pulse oximeter is dropping. Pulse oximeters were not commercialized until 1981/1983 and not in widespread use until at least the mid 1980's.
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)
Answer: The body was fake, made by the scientists at Hawkins Lab in an attempt to cover up his disappearance and the existence of the Upside Down.