Wlan connectivity issues

[sure_not]

I have a Problem with the Wlan on my Xperia XZ (F8331).

The 2,4GHZ Network gets only 3-4mbit (all other devices ~30mbit)

The 5GHZ Network connects and disconnects all the time, or doesnt connect at all and i have to be really near the router to get the 5Ghz network running.

The "selftest" on the phone says there is no Problem with the Wlan.

My Internet is guaranteed 200Mbit @lan, 30mbit @Wlan.

All other devices (smartphones, tablets, SmartTV, Gaming PC etc...) get the full speed and the router was checked by a technican.

Sorry for my bad english.

[Basti881]

Good evening

I had the problem that I could not connect to my WLAN. The connection was never properly built and all other networks in the area disappeared. 

I have now found out that the WPA2 encryption is the problem. Using the WPA encryption now works the connection between the router and the mobile phone.