Why IPv6 not work when I using mwan3?

My English is not good.
Phicomm K2(PSG1218)
LEDE SNAPSHOT, r4675-e5e6045(Sat Aug 5 10:31:29 2017)
mwan3 - 2.6-1

I need to specify an IP address through the specified interface, so I use mwan3.
But when I started mwan3, IPv6 doesn't work, my computer cannot ping LAN(br-lan) IPv6 gateway, the whole IPv6 doesn't work.
When I stopped mwan3, IPv6 is working.
What's the matter?

Hello luxietian

If you don't want to use mwan3 on ipv6 you have to set the family option in the interface configuration to ipv4