Unexpected Disconnection - direct back to login screen, no error message

Hello GGG Team and fellow exiles,

I am experiencing a very consistent and frustrating disconnection issue in Path of Exile 2 that makes the game almost unplayable. The problem started recently, even though the game worked fine for me before.

Detailed Description of the Issue:

While playing, the game runs completely smooth with stable and low latency. Suddenly, without any warning, lag spike to 5000+ ms appears for a split second, and the game immediately disconnects and kicks me straight back to the login screen. No error message.
The disconnection happens extremely consistently every 5-6 minutes, like clockwork, regardless of what I'm doing (mapping, hideout, town, etc.).
Other applications on the same computer (YouTube, Netflix, live streams, large file downloads) work perfectly without any issues.
All other devices in my house (20+ WiFi devices) also have no network problems.

Standalone client (non-Steam version)
ISP: T-Mobile Home 5G
Connection: WiFi (I have also tried wired connection directly to the T-Mobile gateway, same issue)
Location: California, USA
OS: Windows 11
Graphics: RTX4070


Troubleshooting Steps I Have Already Tried (All Failed):

1.Fresh reinstall of the game
2.Changed networking_type in production_config.ini to predictive, lockstep, and back to auto
3.Switched Renderer between Vulkan and DirectX 12
4.Cleared Shader Cache + changed Shader Cache Size in NVIDIA Control Panel back to Driver Default
5.Reset network stack (netsh winsock reset, ip reset, flushdns)
6.Used Cloudflare Warp (made it worse, disconnected in under 1 minute)
7.Restarted T-Mobile gateway multiple times.
8.ran as administrator, disabled firewall/antivirus temporarily, high performance power plan, disabled network adapter power saving, etc.

None of the above steps made any meaningful difference. The issue remains the same, stable gameplay → sudden 5000+ ms spike → instant return to login screen every 5-6 minutes.
This is clearly not a general internet problem, as everything else works fine. It feels like a session timeout or client-server connection maintenance issue that is particularly triggered on my setup (T-Mobile 5G + POE2).
I never had this problem before. It only started happening recently.
Has anyone else experienced the exact same?
Any help or further troubleshooting steps would be greatly appreciated.

Thanks.