Constant connection issues during Frontlines

[KeyKanon]

And only Frontlines. I get the 90000 error, I almost never get this error outside of Frontlines, but once I enter Frontlines, it's happy to show up, often as soon as the match begins.

Time: All times of day
Frequency: Averages around two per Frontlines game, sometimes zero, but it was an instance of 6 in my last game that made me come here.
World name: Excalibur
Character name: Kanon Haruka

It was not always like this for me, only recently, I don't have the exact day it started, but I doubt it was any earlier than 2.38.
I find this to be a pretty serious issue, since it's putting the rightful victory of 23 other players in jeopardy if it happens at a key moment.