Super Smash Bros. Ultimate Has a Game-Breaking Bug on Switch 2

Summary

Nintendo advises avoiding Mii Fighters in online matches on Switch 2 until a bug is fixed that causes online matches to crash.
In addition, Mii Fighter thumbnails may not save accurately, impacting player immersion.
The developers promise an update to resolve the issues soon.

Nintendo is warning Super Smash Bros. Ultimate players against using any Mii Fighters in online multiplayer matches while the developers try to sort out a game-breaking issue. There are a couple of new problems with Mii Fighters in Super Smash Bros. Ultimate, but Nintendo assures fans that both will be addressed quickly.

There are nearly 30 launch games available on Nintendo Switch 2 as of the new console’s release on June 5, 2025. Super Smash Bros. Ultimate isn’t among that number, but it is still playable on the Switch 2 for those who have a copy of the original Switch game, thanks to the new console’s backwards compatibility.

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While that ease of access is a nice touch for fans, an unexpected error regarding Super Smash Bros. Ultimate‘s Mii Fighters is causing Nintendo and developer Bandai Namco to take action. As originally pointed out by Twitter user OatmealDome, Nintendo’s Japanese support website reports that Mii Fighters are causing problems in online matches, potentially triggering a bug that kicks everyone out before a match even starts. This problem seemingly only occurs when one player is on a Switch and the other is on a Switch 2, and while developers are working on a fix, the website requests that players avoid using Mii Fighters in online matches until further notice.

Super Smash Bros. Ultimate on Switch 2 Has a Big Mii Fighter Problem

A second, somewhat related problem concerns Mii Fighter thumbnails when one of these characters is created or edited while the game is being played on a Nintendo Switch 2 console. Some thumbnails do not accurately reflect newly created or edited Mii Fighters’ appearances, which can ruin the immersion for players, considering that the wide variety of costumes for Mii Fighters makes their inclusion a highly customizable part of Super Smash Bros. Ultimate. The solution to this problem seems relatively simple, though, as Nintendo states that players may be able to fix it themselves by reentering the character creator and saving the custom character a second time.

Despite its release nearly six and a half years ago, the crossover fighting game remains quite popular. A report from February put Super Smash Bros. Ultimate in third place on the list of best-selling Switch Games of all time, trailing only Mario Kart 8 Deluxe and Animal Crossing: New Horizons, with more than 35.8 million copies sold. With the Switch 2 now available, there has still been no official announcement of a sequel, but creator Masahiro Sakurai has made past comments indicating that another Smash Bros. game is a possibility.