I am having this problem with just my presentation button. When ever I enable an external display (or simply press Fn + F11 for switching monitors), the keyboard and the track pad locks up.
I tested with an external mouse and it seems to be working fine. At least it functions, but doesn't allow me to click on the menu, or any XFCE item in the panel. Sometimes after a few minutes, the track-pad and keyboard start working, something they don't.
Clicking menu, it responds with the clicked-and-hold animation but that's it. No keyboard shortcuts work, and the only way to get the system back is a force reboot.
FYI, the caps lock and num lock key indicator function when pressed during the lock, so looks like something to do with XFCE desktop. Nothing appears in the ~/.xsession-error during the lock.
Reproducible every time I press Fn + F11, on my Fujitsu A514, 8GB DDR3 running i3, Debian Stretch/testing on Kernel 4.3
I managed to reproduce the exact scenario on Debian Jessie, XFCE 4 but lack the details as I re wiped the system since.
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