I'm having an issue with a Wii U where it has occasional difficulties matchmaking players (the error codes start with 118-05XX). I play Splatoon in my spare time and I spend most of my time in the multiplayer aspect of it. I can usually play for about ten minutes before it decides to either carry on working as normal or throw up the error either in the lobby or during a match.
I feel it could be an NAT issue but the Wii U's internal IP address is in the DMZ. Anything I could do to fix this?