Unstable 5Ghz Wifi connection

Hello,

Please help me out regarding what the problem could be with my settings. My problem is that while the 2.4Ghz network is stable, the 5Ghz network, basically with the same settings, is not, it disconnects my phone two times an hour in average (Android). I also frequently the “wlan2:data from unknown device XXXX sent deauth”, it’s basically flooding my logs - very frustrating.

The export of the settings of my 5Ghz network:

set [ find default-name=wlan2 ] band=5ghz-a/n/ac channel-width=20/40mhz-Ce country=
hungary disabled=no distance=indoors frequency=auto frequency-mode=
regulatory-domain mode=ap-bridge ssid=fortress5 wireless-protocol=802.11

I’ve tried setting the frequency to a fix one, still the same. What can I try? Please give me a hand (I thought of trying another frequency mode, adjusting the number of HW retries and such, but I have no prior experience with them so I’m open to suggestions). I’ve attached a few more screenshots that may help, please let me know if you need any more information. I’m using the latest RouterOS.
2017-04-01 23_14_39-benny@192.168.88.1 (MikroTik) - WinBox v6.38.5 on hAP ac lite (mipsbe).png
2017-04-01 23_15_04-benny@192.168.88.1 (MikroTik) - WinBox v6.38.5 on hAP ac lite (mipsbe).png
2017-04-01 23_14_14-benny@192.168.88.1 (MikroTik) - WinBox v6.38.5 on hAP ac lite (mipsbe).png

Hello,
I came looking for anything similar to what I’m seeing - since upgrade to latest (6.38.5) I have a customer complaining about frequent drops of the wifi, definitely a new problem. Can you share what firmware you’re running? I just downgraded customer to 6.37.5 and haven’t heard yet whether that resolved issue. Customer having problems on andriod phones, Kindles and Windows laptop (Dell).