I saw this too on my first installation of the previous Alpha, it was fixed by doing one more reboot.I just updated my AC86U from 384.17. Everything is working alright, however there is something in the webinterface I did not mention in 384.17.
On the right top corner there is now an icon to adjust the adaptive QoS. In the menu on the left there is an option "Open NAT" without an icon before it.