Comment 104 for bug 1335492

I struggle with a similar behaviour with xubuntu 15.04, but it might be a different bug related to two monitors with different resolution. Icons cannot be positioned outside of size of the smaller monitor and only on the primary monitor (although this is the larger one). If you change the icon size you can move the icons but there position is lost on log out.

Should I open a seperate ticket?

More details:
With standard settings everything seems to work fine, mirror is activated and I see one desktop on both monitors. Since one montior has a higher resolution the desktop is scaled on this monitor (and it is a bit stretched). Moving icons on seems to work fine. With a fresh user I could reproduce:
* mirrored monitor - everything works
* Display -> uncheck "mirror displays"
* moving icons works only in upper left area of the primary monitor (size of the secondary monitor)
* change Desktop settings -> Icons -> Icon size by any number of pixels, now you can move the icons everywhere
* log out, all icons jump back to positions of before chaning icon size

I use the latest PPA version:

$ xfdesktop --version
This is xfdesktop version 4.12.2, running on Xfce 4.12.
Built with GTK+ 2.24.27, linked with GTK+ 2.24.27.
Build options:
    Desktop Menu: enabled
    Desktop Icons: enabled
    Desktop File Icons: enabled