Intermittent ipv6 connection loss with TR862G (comcast's firmware)

lolipoplo

So the docsis is in bridge mode and ipv4 has been flawless.

I see this modem mentioned a few times here. but this issue might be a funny one

ipv6 takes time to get dhcp6 response from docsis, but it does eventually (seems to only work shortly after docsis reboots. If i try to release/re-lease, it almost never responds iirc)
continuous ping6 to google's dns happens like this: 80% continuous success followed by 20% continuous no reply, so on and so forth. This happens for both clients behind pfsense (started with 2601::) and pfsense on WAN int (2001::)

tcpdump on WAN implies icmp6 are out of the gateway with correct src & dest addrs. Firewall issues are ruled out (I haven't changed any rules since installation, pflog0 doesn't show blocking either)

IPv6 was totally fine when the docsis was the gateway. So my preliminary conclusion is that it doesn't work correctly somehow in bridge mode for ipv6

To further eliminate variables, I will set up a linux host directly attached to the docsis and run ping6 overnight.
but if any of you has encountered similar issues please inform.

Thanks

Update1 -------
An 8-hour test from a client behind pfsense has seen the loss dropped to around 8%

Update2
a single host connected to the docsis has consistent 100% ping response for 16 hours

Update3
even when outgoing ping has no response, pinging from my phone on LTE still reaches the WAN interface, although replies echoed, they don't reach back

RESOLVED---------------------------------------------------------------------
The gateway simply doesn't work correctly in bridged mode. I replaced it with a CM500, the ipv6 issue is resolved