Wavlink wl-wn570ha, 5ghz not working properly

Hi,
the 5ghz on Wavlink wl-wn570ha is very unstable. I've played a bit with configs but cannot find what is causing this.
Has anyone encountered this problem and what is the fix?

Yes, there are some problems with this device.
https://forum.openwrt.org/search?q=wn570ha1