Yeah. Something is very wrong here.
airmon-ng start wlan0

Found 2 processes that could cause trouble.
If airodump-ng, aireplay-ng or airtun-ng stops working after
a short period of time, you may want to kill (some of) them!

PID	Name
709	dhclient3
14665	dhclient3
Process with PID 14665 (dhclient3) is running on interface wlan0

Interface	Chipset		Driver

wlan0		AR9001/9002/9271		usb (monitor mode enabled)