Factual error: When Dustin's toy collection "comes to life" (thanks to Eleven), one of the robots is the Transformer Ultra Magnus. Though it appears to be modified with a motorized engine that the actual toy didn't have, that's not the mistake, as there no reason Dustin couldn't have modified it. The error is that the season is set in July 1985, but Ultra Magnus wasn't released in the U.S. until 1986. (Yes, the toy was available as a Diaclone in Japan, but in a different color scheme. Dustin's has the coloring of the U.S. version, and even if he somehow ended up with the Diaclone version, it's highly unlikely he would have repainted a Japanese toy to resemble a Transformer he wouldn't know about the existence of yet, as the 'Transformers' animated movie wasn't released until August 1986).
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)