Steve and Dustin are trying to translate the Russian on the tape recorder. When Robin comes in, Steve is throwing a banana peel on the table, because he is finished with it. In the next shot, he is again eating a banana.
The note Nancy wrote, "Doris Driscoll 4819 Cornwallis Rd, Disease, Rats" previously doesn't match the note she looks at now.
Steve throws his empty banana peel on the table in the back of the ice cream store, then is shown seconds later still holding the empty peel.
At 35:35, Robin (Maya Hawke) looks at the camera for a split second as she is closing the sliding partition.
Hopper is eating Honey Smacks. They were still called Sugar Smacks in 1985. The name did not change until 1986.
The phone book gives numbers in the 765 area code. Although this serves central Indiana now, it did not exist until 1997; in 1985 it would have been area code 317.
The 'Sharp' brand cash register at the Scoops Ahoy ice cream shop is a clear mid-2000s model, made long after the 1985 setting.
Robin states that Dustin and Steve can't translate the Russian recording because they hadn't figured out that Russian uses a different alphabet. It makes no sense at all, since it would be the first thing you would realize when you open a dictionary. Also, the Cyrillic - Latin correlation had already been written by them on the white board.