This has been happening for days now for me too. Starting on Tuesday whenever I go to a different area or fight in a dungeon/trail/raid. Basically, as soon as I start fighting I get an 90002 error code after disconnecting. I can play fine in the over world but cannot do a single fight at all in dungeons and such.
Seriously, load into the fights fine. Walk up to the enemies fine. And as soon as I'm 5-10 seconds into the fight I lose my connection.
It is getting tiresome to even try playing.