The powersaving option in the NetworkManager seems affect the system, disabling will stop the disconnection happen.
vi /etc/NetworkManager/conf.d/default-wifi-powersave-on.conf
[connection]
wifi.powersave = 2
where:
# Values are 0 (use default), 1 (ignore/don't touch), 2 (disable) or 3 (enable).
See also:
https://gist.github.com/jcberthon/ea8cfe278998968ba7c5a95344bc8b55
