Bug Report: RAX120 IPv6 not assigned to mobile devices (iOS/Android) in DS-Lite mode

Model: RAX120 (RAX120-100JPS)
Firmware Version: 1.2.10.56
ISP: Rakuten Hikari (Japan)
Connection Type: DS-Lite (Xpass)

Issue Description:
I am experiencing a critical issue with IPv6 address distribution when using the DS-Lite connection type on my RAX120.

While Windows 10/11 PCs can successfully obtain IPv6 addresses and access the internet via IPv6 (IPoE), all mobile devices (iOS and Android) fail to receive an IPv6 address. As a result, native IPv6 communication is completely unavailable on smartphones and tablets.

Technical Details:

1. In the Web GUI, when "DS-Lite" is selected as the IPv6 connection type, the options for "IP Address Assignment" (such as Router Advertisement/SLAAC or DHCPv6) are fixed/locked. Users cannot manually adjust these settings.
2. It appears that the router is not correctly sending Router Advertisements (RA) required for mobile devices to obtain IPv6 addresses via SLAAC, whereas Windows might be using DHCPv6 to get its address.
3. This issue persists even after updating to the latest firmware (1.2.10.56) and performing a factory reset.

Request:
Since mobile devices rely heavily on SLAAC for IPv6, I request the development team to investigate the RA (Router Advertisement) behavior in DS-Lite mode. Please provide a firmware update to unlock the IPv6 assignment settings or fix the RA distribution logic so that mobile devices can correctly obtain IPv6 addresses.

Thank you.