Other mistake: Season 2, Episode 20: "To the Lighthouse" - In the flashbacks to the jungle, John is considerably younger. Sarah however, is not. Adults don't change nearly as much as a child would in the same time period, but this is a pretty big jump back in time. John is only a child in the flashbacks, putting Sarah in her mid to late 20s. Yet she still looks 35 and even has the exact same skin and facial structure.
Other mistake: When Sarah puts Marty on the bus on his way home he steps onto the first step and turns to face Sarah as the door closes and the bus departs. It is against the law in California for buses to begin moving until passengers are on the main deck of the bus (one step up from the boy). This law was enacted after a child fell from the entry step of the bus (exactly where Marty stood), the doors opened and they were run over by the bus. California operates a zero tolerance policy on this matter; drivers know that a single infraction will result in the loss of their commercial drivers license and is taken very seriously by all drivers, without a single infraction having been reported in years.