Continuity mistake: The mini Puft makes a hole in the marshmallow bag between the letters H and M. In further shots the hole is fixed and it's now between the A and the L.
Continuity mistake: While driving around the city, Trevor wonders if the ghost wasn't really a racoon. Podcast has his ecto-googles on his head, but a shot later, when Trevor suddenly stops, he has them on his eyes.
Continuity mistake: When Gary is testing the trap on the car, he puts his hand very close to it. A shot later it's further away, and he's reaching for the trap again.
Other mistake: When Gary is about to test the trap check the bus door on the right: there's a reflection of what seems to be his shirt, but it's a long sleeved wrinkled shirt, not the short sleeved he's wearing. What's even more bizarre: when Gary moves around, the reflection stays completely still and, drumroll, a shot later, from the very same angle, the reflection disappears. Either it was a crew member hiding, or a CGI-made reflection placed to hide some unwanted crew or equipment reflection.
Continuity mistake: When Gary and Phoebe are trying to open the trap the two cables hanging down the fender and bonnet are either close together or apart, depending on the shot.
Continuity mistake: At Walmart, when Gary finds the sentinel his eyes are looking down. There's a close-up of him slowly looking upwards and finally staring at the creature. Shot changes, and he is looking down again and repeating all previous movements.
Visible crew/equipment: When Gary opens the trap next to the 2 school buses, he is wearing a cable attached to an earpiece on the right side of his head. The kind of cable actors wear to receive instructions from the crew. There's no reason plot-wise for him to be wearing it (he isn't receiving any instructions from the kids, who are right next to him).
Character mistake: There are signs out front as the Spenglers arrive at the dirt farm. One of the signs is a call back to a scene in Ghostbusters 1984. In the scene, Ray quotes the book of Revelation: "And I looked, and he opened the sixth seal, and lo, there was a great earthquake. And the sun turned black as sack cloth, and the moon turned blood." When Finn Wolfhard reads it he misquotes the line saying "The sun became as black as cloth."
Continuity mistake: Trevor is driving the Ecto-1 and complains that Podcast is breathing on him. We see Podcast very close to him. The shot cuts and Podcast is now further away.
