Factual error: Early in the movie we see the newspaper dated "Sunday, March 14, 1987". March 14, 1987 was a Saturday, not a Sunday.
Factual error: In the final surfing scene, Cody and Z are surfing, presumably, off into the sunset. However, being on the north shore (given Z's remark a few moments before), that would mean the wave is rolling to the south which would put the sun toward the east not the west. (01:20:00)
Factual error: The restaurant Joe opens and his apartment at 1 Charles are actually less than a city block apart, so there is no need to drive across Boston to get there.
Factual error: Karl Wolfschtagg's Olympic uniform should have read 'DDR' (Deutsche Demokratische Republik, the German name) rather than 'GDR', the English name for East Germany. Olympic country names are customarily rendered in their native language.