Kubuntu SDDM kills keyboard

[Xen]

I stopped SDDM using systemctl stop sddm from within KDE this time and 
expected to be returned to a TTY as usual.

It took away my keyboard and I had again no way to log in to a tty and 
restart it.

It also took away the display like when it had gone to standby in a live 
session (the monitor).

It could be related to multi-monitor but this is what it is.

For the second time I have had to kill my computer and reboot it while 
it was doing something important.

This has never happened to me before, also not before when I was doing 
the same multi-monitor using the same graphics card.

Today it's a newer kernel (4.10 vs 4.4) and I don't know what else has 
changed.

A different motherboard, yes.

There are no weird messages in journalctl from the previous boot.

Just sddm shutting down, that's it, and my session being killed, which 
is normal.