When you update your firmware, Nintendo includes information on all the latest updates for games, so thats how it knows your game is out of date. If a game was updated after the firmware 11 release, then it wouldn't know you need an update. If you are already banned anyways, click update game. I bet it won't be able to and stealth mode will block it. For system updates, if a newer game has the newer firmware built into the XCI, thats how it knows. I know you said that you trim your XCI, but from what I understand, trimmed XCI just trims off the "blank data" or something like that, so the updates probably aren't deleted. Also, maybe Stealth mode's DNS servers went down. I always thought if the DNS servers went down then the Internet just wouldn't work and the network wouldn't stay connected, but I could be wrong about that. Maybe it reverts to default DNS. I would consider putting
90DNS servers in your internet settings as a backup, because if
90DNS servers go down, then the Internet and network connectivity just stops working because they have both a primary DNS and secondary DNS.