First revert Yun back to factory default (AP mode)

nano /root/setmonitor.sh
#!/bin/ash
uci set wireless.@wifi-iface[0].mode=monitor
uci set wireless.@wifi-iface[0].hidden=1
uci delete wireless.@wifi-iface[0].encryption
uci delete wireless.@wifi-iface[0].ssid
/sbin/uci commit wireless
wifi down; wifi up
chmod 755 /root/setmonitor.sh
/root/setmonitor.sh
iwconfig

lo        no wireless extensions.

eth1      no wireless extensions.

wlan0     IEEE 802.11bgn  Mode:Monitor  Frequency:2.462 GHz  Tx-Power=17 dBm
          RTS thr:off   Fragment thr:off
          Power Management:off

eth0      no wireless extensions.

Mode:Monitor

backup system wide setting: 

uci export > /root/monitor.conf

whenever you need restore it:

uci import </root/monitor.conf
reboot