Not sure if this has been mentioned, but since the release of v1.6 I've noticed when I try to make changes to my triple screen settings (like bezel width for example) then they cannot be saved. You can click on the value you previously had and type in new data, but when you click off it, it reverts back to the old value.
This is a long-standing bug... You'll want to adjust settings within the triplescreensetting.ini file directly, then set the file to Read Only.
@eSTee3 It worked fine for me before. It only became an issue for me around the time v1.6 came out but maybe that's just a coincidence.