So it looks like my games are randomly changing language to Japanese. It's happened to 2 games now, Luigi's Mansion and Pokemon Bank.
- Luigi's Mansion is a rom that I access through Gateway mode via my Gateway cart. Bank is a regular app
- Pokemon Bank was a regular download from the eShop.
- Luigi's Mansion was completely random.
- Bank happened a few times after I tried to connect to Bank with a relatively poor WiFi connection.