@Kevin_Z I installed the beta firmware and then switched to Access Point mode. That does seem to work, but I'm not able reach the router anymore. http://tplinkwifi.net does not work. Neither does...

@Kevin_Z Thanks. I received the link and will give a try. I'll report back my findings here.

@Kevin_Z During the setup I tried setting it to access point mode, but than it froze on me and I couldn't access the router at all anymore. Then I did a factory reset and then I didn't dare to try it...

@finder Thanks for the feedback. I already set the channel and the width. No real big improvement unfortunately.

@Kevin_Z It seems to be a bit more stable, but every once and a while it still stops working. The LED I mean is the square one on top of the router. I did notice that when the 5GHz wifi stops working...

That sounds indeed as exactly the same. Unfortunately I haven't found a cause nor a solution yet. But I do have to mention that the time it is working is getting longer. In fact, since my post 2...