IPv6 and few clients keep disconnecting

[hellreturn]

As soon as I enable IP V6, few devices keep disconnecting every 1-3 minutes. Is their anyway, I can figure out where the issue is? I see this in logs - 2.4 and 5Ghz both have same issues.

Router: AC3100
Firmware: 384.16

Apr 13 16:14:24 syslog: WLCEVENTD wlceventd_proc_event(420): eth1: Auth zzzz, status: 0, reason: d11 RC reserved (0)
Apr 13 16:14:24 syslog: WLCEVENTD wlceventd_proc_event(449): eth1: Assoc zzzz, status: 0, reason: d11 RC reserved (0)
Apr 13 16:14:24 syslog: WLCEVENTD wlceventd_proc_event(420): eth1: Auth yyy, status: 0, reason: d11 RC reserved (0)
Apr 13 16:14:25 syslog: WLCEVENTD wlceventd_proc_event(449): eth1: Assoc yyy, status: 0, reason: d11 RC reserved (0)
Apr 13 16:14:25 syslog: WLCEVENTD wlceventd_proc_event(386): eth1: Deauth_ind xxx, status: 0, reason: Class 2 frame received from nonauthenticated station (6)
Apr 13 16:14:25 syslog: WLCEVENTD wlceventd_proc_event(420): eth1: Auth xxx, status: 0, reason: d11 RC reserved (0)
Apr 13 16:14:25 syslog: WLCEVENTD wlceventd_proc_event(449): eth1: Assoc xxx, status: 0, reason: d11 RC reserved (0)