Dual monitor setup - Why my offset isn't kept?

Pardon my globbish.

I’m using 2 monitors, landscape+portrait mode. At startup, the latter is well oriented but not properly offset.

This is my .config/openbox/autostart:

# écrans dell+philips
xrandr --output DP1 --off --output DP2 --off --output HDMI1 --off --output HDMI2 --mode 1280x1024 --pos 0x0 --rotate normal --output VGA1 --mode 1024x768 --pos 1280x0 --rotate left --right-of HDMI2  --output VIRTUAL1 --off &

# required for xfce settings to work
xfsettingsd &

# start the panel
tint2 &

# load wallpaper
nitrogen --restore &

Maybe some setting is overriding this one.
But where to look at ?

Try running xrandr after xfsettingsd.

Some news: I removed the xrandr line from my autostart.

During lightdm greeter,/etc/lightdm/Xsession sources ~\.xprofile which I’ve edited to call xrandr with the correct setting. And as a matter of fact, the screens behave well just after login.

But when openbox starts, the offset falls back to zero.

To be continued.