Hi RMerlin, any idea how do I go about solving the NAT loopback on my AC87U?
When I first flash it with this firmware, it does not work. Then I left it running for a few hours, magically it works. Then few hours later, it does not work again.
Are there any settings that I need to tweak? Any logs to check for signs of misconfiguration?
First thing to test is to determine if the issue could be the DDNS not properly updating. Do your tests using your WAN IP (obtain it using a website such as whatismyip, or from the router's settings page).
Try disabling Adaptive QoS and AiProtect, in case these could interfere (they are closed source, so it's impossible to tell for sure if they interfere or not).
If you use UPnP, make sure you set the allowable ports from 1 to 65535 (default is only 1024 to 65535, which does not work properly with WHS).