Can't connect to WiFi, only if wireless restart then problem reappear after it disconnect

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AC68U router, it started about 3 days ago, devices cannot connect to 2.4GHz or 5GHz if any disconnects. Devices just try to connect and says 'connecting' then it just does not connect.

It connects only if wireless restart (by either turn router off & on or change settings that lead wireless to restart), and then problem reappear again if any device disconnects and try to connect again after about 30 minutes after the wireless restart process.

[so, if I restart the wireless, everything will work good. But after about 30-50 minutes, if you disconnects, you then will not connect again at all].

the same on wired connection.

I have upgraded Merlin firmware to latest (380.62_1), and reset the router, nothing helps. My router settings are always default except QoS and AiProtection

Any way to solve this problem?

Thanks

Edit: Can anyone change the title, (sorry its a mistake): "Can't connect to WiFi, only if wireless restart"

 

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Problem solved, I did not figure our what is causing this problem though. I just shutdown router for about 2 hours and did a hard reset.