Comment 5 for bug 1471254

I got a similar problem breaking at mate-settings-manager.c:maybe_activate_plugin and single stepping really helped in finding the problem. In my case this was caused by the monitors.xml in /etc/mate-settings-daemon/xrandr.
This one is however recreated which makes the daemon fail again on next start.

Also strange: I can only start the daemon with sudo, starting it with user rights will make it hang forever after it got the DBus.

I tried to change values in the xml till it worked and found that "<serial>0x00000000</serial>" for one of the 2 monitors was the problem. In this case this is the laptop screen itself. Setting the serial to anything non-zero made it work.

Maybe this should be caught in the daemon or xrandr?