A strange thing happened. After upgrading, pppoe0 does not get the IPv6 address (DHCPv6 PD normally gets the IPv6 prefix).
PPPoE is configured as follows (account password is hidden):
pppoe pppoe0 { authentication { password pass user userid } default-route force description ISP dhcpv6-options { prefix-delegation { interface br1 { address 101 sla-id 2 sla-len 8 } interface br2 { address 101 sla-id 1 sla-len 8 } length 56 } } firewall { in { ipv6-name WAN-IN name wan } local { ipv6-name WAN-LOCAL name wan-local } } idle-timeout 30 ipv6 { address { autoconf } enable } mtu 1492 source-interface eth5 }