Consultants

I don't understand why it's so difficult for movies about a certain topic, where the main character(s) is meant to be an expert on that topic, to themselves employ experts on that topic during filming to ensure no obvious errors are made.

For example, if you're making a movie about snowboarding, hire a professional snowboarder to consult. If you're making a movie about deep sea fishing, hire an experienced deep sea fisherman to consult. If you're making a movie about birds, hire an ornithologist as a consultant, so the filmmakers don't just randomly to replace a particular plot-relevant bird with a totally different bird, and just call it a day.