Sexual assaults have been covered up by literally every organization that has ever had people in it. This isn't a sport issue, the Catholic Church has been doing it for thousands of years. Hell even families have covered up this kind of thing by paying people off for all of known history. Why are you surprised it exists anywhere? Fining people isn't going to stop that either, even if you started jailing executives from organizations if it happens all you would see is organizations shutting down, there's nothing they can do to prevent it 100% of the time no matter how much they "change their culture" .

So what's your solution? How do you prove something that happens only inside someone's mind?

You could video tape every single sexual encounter from start to finish, require both drug and alchohol tests prior to ensure competence, have the people involved make sworn statements before and every 5 minutes during, and it still wouldn't hold up if one party said they felt pressured because they thought the person would hurt them (physically, mentally, emotionally) outside the encounter if they didn't go through with it.

The system doesn't work.

So either sex has to stop entirely, people need to risk going to jail every time they have sex, or we need to change the system.