Hello new user here.
I managed to flash OpenWrt 18.06.2 on my ap. I'm planning
on having coova-chilli on it. My nanopi neo2 with freeradius is ready to serve.
I'm trying to configure my AP, but having a hard time.
My pc keeps disconnecting as if there's a contention between
the unifi ap and the router (RT-A66U with wifi disabled).
If I hard reset the ap it doesn't exhibit disconnect but when make changes with lUci and saved configuration it start to disconnect after a few minutes. I'm stump. I've reverted to stock firmware and back again to OpenWrt and still the same.
Any pointer on what to check and where would be greatly appreciated.
Edit:
Is it normal that I have the AP set with static IP but my router still sees it as DHCP?
Edit2:
Note that the disconnect does not happen if the AP is not plugged to the router.
Edit3:
I think I may have solve the flip flop disconnect/reconnects of my NIC, but I'm not exactly sure why it happens.
I happened 
to check my syslog and saw this.
Feb 14 09:09:04 darkstar dhcpcd[2561]: eth0: fe80::feec:daff:feb3:ba0c router available
Feb 14 09:09:04 darkstar NetworkManager[1122]: <warn> [1550106544.6750] device (eth0): Activation: failed for connection 'Ethernet connection'
Feb 14 09:09:05 darkstar NetworkManager[1122]: <warn> [1550106545.2119] (pid 2561) unhandled DHCP event for interface eth0
Feb 14 09:09:06 darkstar NetworkManager[1122]: <warn> [1550106546.3417] dhcp6 (eth0): the dhcpcd backend does not support IPv6
Feb 14 09:09:06 darkstar NetworkManager[1122]: <warn> [1550106546.4251] device (eth0): Activation: failed for connection 'Ethernet connection'
Feb 14 09:09:06 darkstar NetworkManager[1122]: <warn> [1550106546.9619] (pid 2576) unhandled DHCP event for interface eth0
Feb 14 09:09:08 darkstar NetworkManager[1122]: <warn> [1550106548.5314] dhcp6 (eth0): the dhcpcd backend does not support IPv6
Feb 14 09:09:08 darkstar dhcpcd[2590]: eth0: DHCPv6 REPLY: Not On Link
Feb 14 09:09:08 darkstar NetworkManager[1122]: <warn> [1550106548.5583] device (eth0): Activation: failed for connection 'Ethernet connection'
Feb 14 09:09:09 darkstar NetworkManager[1122]: <warn> [1550106549.0952] (pid 2590) unhandled DHCP event for interface eth0
Feb 14 09:09:10 darkstar NetworkManager[1122]: <warn> [1550106550.7296] dhcp6 (eth0): the dhcpcd backend does not support IPv6
Feb 14 09:09:10 darkstar dhcpcd[2603]: eth0: fe80::feec:daff:feb3:ba0c router available
Feb 14 09:09:10 darkstar NetworkManager[1122]: <warn> [1550106550.7668] device (eth0): Activation: failed for connection 'Ethernet connection'
So I checked my eth0 connection info on NetworkManager and set ipv6 to ignore then restart NetworkManager and the constant disconnect of my NIC disappear. I can now use ssh again 
It's odd that I now seem to have two network connections,
but if I manually disconnect my Ethernet connection and manually reconnect the original problem occurs. I had to restart the network manager service get it stable again.
Although I'm a linux user I know very little about networking.
If someone could explain why the disconnect/reconnects happen that would be great..thnx.