Hang happend with VGA cable also. I've also checked compton vsync option (changed this to 'opengl' around the time when hangs started). Reverted to 'none', did not help. I also have access to Lenovo e130 laptop packing i3-3217U with similar system installed, and XFCE as the environment (I use stripped LXDE on mine). And it does not hang. Now i've booted from my hard drive on e130 to find out if this is hardware issue.