negative geometry position selects wrong side for some users

[Skaperen]

i am running Unity on Ubuntu 16.04.5 LTS with multiple users.

when i have a script launch a program with a negative horizontal position in the geometry option, it works fine in one user and places the script at a horizontal position relative to the right side of the display as intended.. this happens to be the user i needed it first in, so i initially wrote the script under that user. later i had another 3 users copy that script over to their home directories (so that copy would be owned by them. but when i ran it, it placed the window relative to the left side, plus a few more pixels to the right.

the intended position was -1 so it would be just one pixel away from the right end. but it ended up about 16 pixels from the left end. the program is "gnome-terminal". when i intend to position it relative to the left side, it always works on all users. i usually have 12 logged in users at a time, switching them as needed.

does anyone have any idea why it would work right for one user and work wrong for another?

[again?]

If it's in Unity it's may have to do with the number of virtual desktops for different users.
Do some tests using

wmctrl -d
xwininfo

[Skaperen]

all 12 users have 9 virtual desktops in a 3x3 arrangement.