Phenomenon Observed on the Target Device

We are experiencing the following issues with the device. I personally believe this is related to the firmware. We have tested with two firmware versions: the latest one and the one prior to the update.

Environment Used
Windows 11 (Desktop PC)

Motherboard: ROG B550-A
Note: All drivers have been updated to the latest version.
Testing was conducted using a wired connection only, as there is no wireless LAN.
Windows 11 (Laptop)

Model: Dynabook GA83XW
Note: All drivers are up to date.
Testing was conducted using both wired and wireless connections.
iPhone 14

iOS 18 / iOS 26 beta
Testing was conducted using a wireless connection only.
Testing Environment
After restarting and reconfiguring the HGW (Home Gateway), a restart was performed.
After changing the settings on the BE85, a restart was also conducted (tests were also performed without restarting).
Testing Items
IPv4 Settings: IPv6 Plus / IPv6 Option / MAP-E
Multiple combinations were tested with the following items:

IPv6 Settings: PD Enabled / Disabled
nd proxy / DHCPv6
Verification Results
Note: Only the best connection results are listed below; other results generally indicate no connection.

Deco BE85 (JP)_V2_1.1.1 Build 20241023
IPv4 Setting: IPv6 Plus
IPv6 Setting: PD Enabled / Disabled - nd proxy
Wired LAN (Desktop and Laptop)

Unable to access all IPv4 websites via wired LAN.
IPv6 websites are accessible (e.g., YouTube, Google).
Some IPv4 websites are accessible via wireless LAN (e.g., Discord).
Wireless LAN (Laptop/iPhone 14)

Some IPv4 websites are accessible via wireless LAN (e.g., Discord).
Certain applications experience connection drops and cannot be used.
Deco BE85 (JP)_V2_1.2.0 Build 20250724
IPv4 Setting: IPv6 Option
IPv6 Setting: PD Enabled / Disabled - nd proxy
Wired LAN (Desktop and Laptop)

Unable to access all IPv4 websites via wired LAN.
IPv6 websites are accessible (e.g., YouTube, Google).
All websites are accessible via wireless LAN.
Wireless LAN (Laptop/iPhone 14)

All websites are accessible via wireless LAN.
However, restarting the BE85 causes a rollback to the issues experienced in Deco BE85 (JP)_V2_1.1.1 Build 20241023.
To restore wireless functionality, a factory reset and reconfiguration are required (similar issues may still occur even after reconfiguration).