[Disconnect] Constant Error 900002 [Virgin Media UK]

Issue
Disconnection from client and error 90002 when teleporting or going through any form of loading screen. It also frequently occurs when out of combat, but never during (very peculiar).

Frequency
Five to six times a day, at completely random times. It may go a full day without happening, or it may occur several times throughout the day.

Internet Provider
Virgin Media UK. There are multiple threads on their own forums, as well as here and on Reddit, that detail this exact problem, but none of them offer a solution.

Threads about the same issue:
• An open letter to VM regarding Final Fantasy XIV
• Is anybody here on Virgin Media (UK)?
• Any solutions to the 90002/90001 problem?

Worth noting that I have the 50Mb fiber connection package, which is otherwise extremely reliable in all sorts of games and software - except for FFXIV.

Troubleshooting
Tried resetting the router back to factory defaults; set up port forwarding and firewall; completely reinstall the game; switched from wireless to wired.

Additional Notes
While the game client boots me back to the main menu, everything else remains connected - such as Teamspeak and Discord - and nothing else loses connection. The computer itself also never loses connection to the router.

Upon being kicked back to the main menu, I can immediately reattempt to log back in, although I am greeted by the typical "your character is still logged in" error, which forces me to wait a minute or two.

Final Words
Please help me address this issue. Playing Final Fantasy has become a rather frustrating experience with the constant disconnections. It would be rather unpleasant if this was the reason I eventually stopped playing the game.