it’s been a bug thats been reported numerous times on different topics, see: Randomly disconnecting from games because "Same account launched from different device" - #35 by xarmebx
and I think the issue arises when users are teleported from one place to another or when games are opened and closed quickly. roblox hasn’t fully processed that the game you closed has been closed and it sees it as another experience being open while you are trying to open another experience
it’s frustrating to see a bug that’s been around since 2019 still be an issue today :l