When the two boys are talking in the bedroom, the sweat stains and patterns on Will's shirt constantly changes with different camera angles and cuts.
When Dustin takes a bouquet of roses from Steve and walks away, Steve is seen picking up something from the ground. When Dustin turns around to talk to Steve, there is nothing in Steve's hand.
When Bob is talking to Joyce outside of her house, the position of the windshield wipers on Bob's parked car change positions a couple times. Some shots show them close down by the cowl, other shots show them more towards the center of the windshield.
As Murray Bauman holds the bottle of vodka in his hand, its name on label is clearly misspelled. Its SLOTichnaya, instead of STOLichnaya.
The JAWS one sheet movie poster is not an original release poster or a re-release or an International poster. Every single Jaws poster was dark blue (except 2 very rare versions which were black) and each and every one had a substantial white border. The one in the boys bedroom is black/dark blue to the edge of the poster which none ever had.
When Nancy and Jonathan go to Murray's hideout, the flag in his hallway is hanging incorrectly. The union, or star field, should always be at the top and should be on the flag's own right (the viewer's left).
When Lucas' sister Erica is pouring the syrup on her french toast, she is squeezing a plastic bottle of Mrs. Butterworths. The brand Mrs. Butterworths didn't go to the plastic bottle until 1999 and since this show takes place in 1984, Mrs. Butterworths syrup would have still been in the glass bottle.