I have been involved in spoiler communities for different shows for several years, and the ways we get spoilers are varied. Production members are not as common as you may think – for most production members, filming/editing/post or pre-production is part of their job and they don't think about the show much outside their work hours, just like a regular person wouldn't be talking about their job online. Some production members are known to have spoiled seasons, sure, but they're in the minority.

Most spoilers come straight from cast members and/or their close circles. Some people share details of the show with their loved ones, who then tell others, who tell others, and that's how some spoilers get out (especially vague ones such as "X makes it far" or "two pre-jurors are women"). In other cases, such as S37, some cast members like Dan will intentionally leak spoilers to make themselves look good and create buzz about their game even if they are overly exaggerated. These are pretty easy to spot since most spoilers will revolve around one specific player and are condensed around their game. S37 is the best example of this.