My HG612 was supplied by BT so the default state of the firewall was named "BT" which prevented any access at all. I don't know which of the various firewall settings are default on yours.
The request to drop PPPoE is sent by BT's TR069 server. This is standard practice and plagues everyone on BT as I've already said. It is what led me to unlocking my HG612 in the first place to disable TR069 to stop it happening, as soon as Asbokid's unlocked firmware was available.
Did you use the Mega firmware suffixed by _webgui to unlock yours? That's the one I recommend as it has TR069 disabled by default.