This sounds like a GUI issue with gnome-control-center. Are you able to work around it by tweaking the x/y values in ~/.config/monitors.xml instead?
** Package changed: xorg (Ubuntu) => gnome-control-center (Ubuntu) ** Changed in: gnome-control-center (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to gnome-control-center in Ubuntu. https://bugs.launchpad.net/bugs/2029008 Title: Display positions cannot be accurately set in settings To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-control-center/+bug/2029008/+subscriptions -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs