Journalists sometimes roll a "1" on their fact checks.
If people who failed to research are writing about Dungeons & Dragons, 99 times out of 100 a reference will be made to a "dungeon master" as though it were something that existed in the game world instead of a fancy name for a referee.
The animated adaptation really did have a character called "Dungeon Master". Of course, the series was only loosely based on the tabletop game and it's not as well known, so it's mostly irrelevant. Depending on how charitable you are, the series might itself be considered an example of the trope.
99 times out of 100, this won't be their only egregious mistake, either.
Apparently, Frederic Raphael, Stanley Kubrick's co-storywriter for Eyes Wide Shut, thought that "The trend of RPGs in France has made some victims recently, especially among teenagers [...] What happens, more or less, is that some friends play the roles of the characters of a comic - comic books in France are often "gothic" and erotic, for adults - and in their meetings, they replay what happened in the last issue of the story. Sometimes, the game becomes so extreme that someone leaves the real world to live in the "other world" with an often dangerous fantasy identity, up to murder or (more frequently) suicide". He wrote this in "Eyes Wide Open", a book about his collaboration with Kubrick. And in a single paragraph, there's more errors and misconceptions about Role Playing Games than in entire newspaper articles.
One French magazine had an article about Warhammer 40,000. In it, they showed a picture with the caption of "Ultra-Marines [sic] disembarking from a Rhino." However, the Ultra-Marines [sic] are bright yellow (which would make them Imperial Fists) and the "Rhino" is a Land Raider. In perhaps the worst screw-up in the article, the Orks are referred to as "Tau". For the uninitiated- Orks are huge, green, and muscular, preferring close combat. The Tau are slender, bluish-grey, and hate close combat. Bonus points because the Tau and Orks are, in-universe, mortal enemies (at least from the Tau Perspective. Orks don't really give a damn who's on the receiving end of a choppa).
An epic fail shared by pretty much all the major UK tabloids (at a minimum, the Daily Mail, The Sun, Mirror, Telegraph and Metro all ran the story) about a mother of three neglecting her children and pets because she was obsessed with playing the board game Small World online. Leaving aside the obvious sensationalism (like kids eating cold baked beans with their fingers because the house apparently had tin openers but no spoons, and a thirteen-year-old doing nothing about the situation even when the dogs starved to death and were left to rot on the floor) the biggest issue is that there is no online version of Small World in existence. The closest thing is the iPad version, which you can only play locally, like the real board game. The articles contain accurate images and descriptions of the board game (except for a random shot of Warhammer Online) and links to the parent company, but they have literally nothing to do with the case. It looks likely that the game involved is actually smallworlds.com, a completely unrelated Second Life type of game, a journalist messed up the Google search somewhere, and the mistake propagated from there.
A rather gruesome murder (involving decapitation) in Sweden was touted by the newspapers as the "Vampire Murder" when it was revealed that the victim used to play Vampire: The Masquerade. Predictably, speculants drew up all sorts of wild ideas about ritualistic sacrifices connected somehow to the game. Eventually the murderer was found out, and not only was the game not involved, but the murderer and victim were not connected at all (outside of the actual act, that is). Predictably, the newspapers did not put much effort into retracting their accusations.
This despite V:TM being one of the few RPGs that included a specific "dude, this is pretend, don't forget it for a second, if that starts getting unclear you take a damn break" reminder.
There was another instance in Scandinavia where gravestones had been vandalized in a cemetary near a Vampire LARP, and when questioned by the police, the gamers unwisely joked how they leave petty misdemeanors like that for the Ghouls. In result there was a police officer observing the games for the next several months before they realized what was the deal with the game, and that it had nothing to do with committing religious crimes.
In Malaysia, a television news segment ended up mislabeling an Islamic trivia board game as a European designer board game, possibly due to a combination of uninformed editing and mild religious zealotry.