And yes, based on my testing on my sister's AC1200 v2, it seem like getting heavy corrupted on its flash memory, which might proof that it is the hardware flash memory is having like the old Samsung Galaxy note 2/3, keep corrupting the flash memory over time.

Or, it is a side effect caused by auto reboot, or, bug on kernel handling on flash memory, which can be fixed if heavy tested.

But you know, TP-link unlikely updating/fixing this router anymore.
https://www.xda-developers.com/hard-brick-b...ed-ics-kernels/

---
Anyways, the result is, I can't get one of my device connected to the Internet, keep having handshake failed, and IPv6 having failed packet fragmentation due to unknown by using chrome to open this.
https://test-ipv6.com/

Only Chrome and native app that not using webview + custom webview like UC or TBS + https can access.


But then, another day, after another reboot of the router because it hang on connecting to the internet, this issues magically gone on this phone.
---
And yes, this phone works on 99% of network, only 2 network found to be failed on handshake(I suspect because of heavy modified webview upgraded to normal Google webview, and not using trichrome or chrome as webview is causing it).

As this phone works on another AC1200v2, so I guess the router is corrupting the packet in some ways.
Or, bad firewall(that SPI Firewall) handling wrongly the packet, only on that phone.


Sadly I lacking laptop to open hotspot and do some wireshark to identify the issues, so I guess, the solution is.

Just recommend my sister, switch to a new router that is stupidly stable and simple enough, again and again.