LEDE 17.01.0 @ WRT1900ACS - Problems with WiFi!

1st problem: My devices can't connect above 144.4Mbps at the N band.

2nd problem: At the AC band and under "heavy" load (e.g downloading + video streaming simultaneously), I face random wifi disconnections and router freezes. Sometimes when I manage to disconnect from the router's WiFi, the WiFi LED stays on!

/etc/config/wireless:

config wifi-device 'radio0'
        option type 'mac80211'
        option hwmode '11a'
        option path 'soc/soc:pcie-controller/pci0000:00/0000:00:01.0/0000:01:00.0'
        option channel '36'
        option htmode 'VHT80'
        option txpower '20'
        option country '00'


config wifi-iface 'default_radio0'
        option device 'radio0'
        option network 'lan'
        option mode 'ap'
        option ssid 'WLAN0'
        option encryption 'psk2+ccmp'
        option key 'XXXXXXXXXX'
        option ieee80211w '0'
        option disabled '0'

config wifi-device 'radio1'
        option type 'mac80211'
        option hwmode '11g'
        option path 'soc/soc:pcie-controller/pci0000:00/0000:00:02.0/0000:02:00.0'
        option channel 'auto'
        option htmode 'HT40'
        option txpower '20'
        option country '00'

config wifi-iface 'default_radio1'
        option device 'radio1'
        option network 'lan'
        option mode 'ap'
        option ssid 'WLAN1'
        option encryption 'psk2+ccmp'
        option key 'XXXXXXXXXX'
        option ieee80211w '0'
        option disabled '0'

Is there any solution?
Thank's!

As for the 1st problem (max 144.4 Mbps at N band), it's fixed by adding
option noscan "1"
in the config file.

For the 2nd problem, I think I should wait for a firmware update, the performance at the AC band is buggy.