I have the same issue (http://forum.mikrotik.com/t/issue-with-rb5009-ros-v7-1rc1-dhcpv6-pd-over-pppoe-on-tagged-ethernet-link/151407/1).
It only happens when running pppoe over a tagged vlan. It works on an untagged link.
I have the same issue (http://forum.mikrotik.com/t/issue-with-rb5009-ros-v7-1rc1-dhcpv6-pd-over-pppoe-on-tagged-ethernet-link/151407/1).
It only happens when running pppoe over a tagged vlan. It works on an untagged link.