Constant disconnects

[Packetdancer]

Of course it's our ISP's fault... there's NOOOOOOOOO possible way it has anything to do with the patch, despite it being an issue that's occurred since the patch. It's just one huge coincidence that all of us are having ISP issues since 5.2 dropped. /s

To be fair to SquareEnix, Comcast is demonstrably having an absurd amount of weird problems at the boundary with NTT (on which FFXIV is hosted) right now and has been since about February 20th; the fact that the equipment there apparently had the networking equivalent of a stroke two days after the 5.2 patch is really unfortunate timing, but not necessarily connected to the patch itself. And if you're on Comcast—or a smaller provider that uses Comcast as their backbone connection—I would honestly say the chances that any sort of connectivity weirdness are related to that whole situation are a non-zero quantity.

I mean, my FC-mates who are on Comcast have had a litany of different connectivity issues to FFXIV since 5.2, and what they are seems to vary; the only consistency is that all of the affected on any given night are on Comcast, and literally everyone else in the FC is fine. I don't know whether it's on Comcast's side or NTT's side, but they've had lag/latency, dropped packets and disconnections, streams that just get arbitrarily closed after a certain time because the boundary router seems to think they're no longer needed, etc...

That said, regardless of whether it's the Comcast/NTT boundary weirdness that's affecting you or not, I can totally get that them using the same set of questions to try to get folks back online feels frustrating. But I doubt the tech support folks are finding it any more fun to be able to not provide an answer; based on watching friends who've worked tech support jobs, I would put decent odds on the guess that they don't even have the authority to try to escalate a problem to a dev to look at unless they can tick off a box somewhere that says they've offered all the stock solutions, and that the customer confirmed trying them with no success.

Edit to add: FWIW, if this is the case for you, using a gaming-focused performance VPN—which will route your traffic around the affected boundary—should actually clear the issue up. That's what several friends have done to get around the situation. If it does fix things, the issue is with your ISP (or rather, the route between your ISP and FFXIV's servers); if it does not, then the issue is on the local network (or in FFXIV's network code).

[PeeweeHardwell]

I found the solution for the disconnection every 2 hours, but maybe could be applied to others randoms disconnections with error 90k.
After a lot of test i identified the problem in my end, my router after 2H and 5 minutes had a DHCP release, causing some package lost and the disconnection with the error 90K.
I own 2 router Netgear R6900P and R7000P both router have the same issue, after read in their forum seams to be more people are experiencing the same behavior, with those two router and others due to the firmware is basically the same for must of them.
My solution, log on into the router menu(192.168.x.x) and activate QoS(Quality of Service) this will stop the disconnection every X amount of time, but depending on your connection this can have an impact in your connection. Any way is a good way to isolate yours constant disconnection.
Just activate QoS, apply the change, log off, reboot your router and modem and you should be online again. My advice not to mess with other options in the QoS like prioritize some connection and stuff like that.
I bought the Asus RT-AC68U and i did not have to do nothing, it worked great with no disconnection or other issues.
If anyone need more explanation just ask.