Raspberry Pi loses connection via Wifi

[fabiopedrosa]

I have an RPi 3 running a simple service that pings a public server. But I keep seeing the device going offline and showing this at its console:

root@f70ca89:/var/log# [  241.257918] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
[  241.910237] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
[  241.947894] brcmfmac: power management disabled
[  244.418907] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
[  244.458738] brcmfmac: power management disabled
[  320.095062] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
[  320.701004] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
[  320.724647] brcmfmac: power management disabled

I'm running balenaOS 2.29.2+rev2 (development) with supervisor 9.0.1

How can I ensure the wireless connection is kept online?