Millions of gamers tune in to Twitch every day to watch their favorite gamers play and provide colorful commentary. But the platform is coming under increasing scrutiny, with one watchdog group describing it as “unpredictable.”

Case in point: Last weekend, porn that was tagged “Fortnite” appeared on the Twitch page that formerly belonged to Tyler “Ninja” Blevins, a millionaire gamer and the platform’s biggest star. Earlier this month, Ninja announced he would leave Twitch for Microsoft’s live streaming service, Mixer, so the incident felt a bit like a “jab” for leaving, Ninja said in a video posted on Sunday.

It was an upsetting incident for the star, who serves as a role model to young gaming fans. In a series of tweets, Twitch Chief Executive Officer Emmett Shear apologized to Ninja and said the porn appeared on his page because Twitch promotes live streams on the pages of channels that aren’t currently streaming. The incident led to Twitch suspending its recommendation system, which had clearly been expertly gamed.

In another instance, Kyle "Bugha" Giersdorf, the 16-year-old who won $3 million in the Fortnite World Cup, was swatted on Saturday while streaming on Twitch from his home in Pennsylvania. Swatting is when someone calls in a dangerous emergency at an enemy’s house, such as a hostage situation, sending the SWAT team to knock on their door.

"Yeah, I got swatted ... Dude, they came in with guns, bro. They literally pulled up," Giersdorf said. "The internet is f------ crazy."

Twitch, which is owned by Amazon, is by far the most popular streaming service, with at least 410 billion streaming minutes watched so far this year, according to Twitch Tracker, a site that shares the streaming service’s metrics. That’s on track to outpace the 560 billion minutes watched last year. Amazon bought Twitch for $1 billion in 2014 and it has only continued to grow, especially with the strength of Fortnite.

While it’s unclear who swatted Bugha, both incidents show how the platform can be manipulated for pranks that have the potential to turn dangerous.

“There's no time delay with live-streaming — what gamers say and do goes out immediately, so the content is unpredictable,” Common Sense Media, a children’s watchdog group, wrote in an online guide for parents.

The group adds: “While Twitch is a gamer's paradise, and the overall tone is kept in line by the site's usage rules, there's plenty of age-inappropriate content.”

Clint Kennedy, director of education at PlayVS, a high school esports league, called Twitch “the 800-pound gorilla in this space.”

“We get questions all the time about screen time and educational links to the curriculum and video games and violence. I appreciate parents coming to us with those questions,” Kennedy told NBC News.

With esports becoming even more popular, Kennedy said isolated incidents of platform abuse aren’t his chief concern. He’s instead focusing on teaching young gamers to practice the same “cultural norms” they would on traditional sports teams, which he said will help promote a culture of “healthy gaming.”

That includes teamwork, respecting opponents, coaches and finding a balance between gaming, academics and family life. Ultimately, those values should spill over into the gaming world.

“To be successful, gamers have to follow the processes we build in other activities,” he added. “And then apply them to esports.”