I already tried to change the timeout using dconf, setting it to 0 (infinite).
In fact, gsettings get org.gnome.settings-daemon.plugins.power sleep-inactive-ac-timeout return 0.
I already tried to disable every parameter under org.gnome.settings-daemon.plugins.power but nothing worked.
gsettings list-recursively org.gnome.settings-daemon.plugins.power return:
org.gnome.settings-daemon.plugins.power button-power 'nothing'
org.gnome.settings-daemon.plugins.power sleep-inactive-ac-timeout 0
org.gnome.settings-daemon.plugins.power power-button-action 'nothing'
org.gnome.settings-daemon.plugins.power critical-battery-action 'nothing'
org.gnome.settings-daemon.plugins.power percentage-low 10
org.gnome.settings-daemon.plugins.power priority 0
org.gnome.settings-daemon.plugins.power lid-close-suspend-with-external-monitor false
org.gnome.settings-daemon.plugins.power idle-dim true
org.gnome.settings-daemon.plugins.power button-hibernate 'nothing'
org.gnome.settings-daemon.plugins.power sleep-inactive-ac-type 'nothing'
org.gnome.settings-daemon.plugins.power button-suspend 'nothing'
org.gnome.settings-daemon.plugins.power button-sleep 'nothing'
org.gnome.settings-daemon.plugins.power sleep-inactive-battery-timeout 0
org.gnome.settings-daemon.plugins.power time-low 1200
org.gnome.settings-daemon.plugins.power lid-close-ac-action 'nothing'
org.gnome.settings-daemon.plugins.power notify-perhaps-recall true
org.gnome.settings-daemon.plugins.power percentage-critical 3
org.gnome.settings-daemon.plugins.power percentage-action 2
org.gnome.settings-daemon.plugins.power sleep-inactive-battery-type 'nothing'
org.gnome.settings-daemon.plugins.power time-action 120
org.gnome.settings-daemon.plugins.power lid-close-battery-action 'nothing'
org.gnome.settings-daemon.plugins.power idle-brightness 30
org.gnome.settings-daemon.plugins.power ambient-enabled true
org.gnome.settings-daemon.plugins.power time-critical 300
org.gnome.settings-daemon.plugins.power active true
org.gnome.settings-daemon.plugins.power use-time-for-policy true