Leap & KDE plasma5.

Yesterday my desktop froze several times (my system has been quite stable for the past week). None of the keystrokes that I am familiar with worked but I was able to go to a virtual terminal. When I went back to KDE with C-A-F7 I had a black screen and moving mouse arrow. The solution I used (did not try C-A-D) was to go to a virtual terminal and execute shutdown.

I did not think to examine some log files from the virtual terminal, I'll do that if this happens again. Looking back in journalctl this is what I see prior to switching to a virtual terminal to shutdown

Code:
Dec 07 23:36:26 linux-shpr dbus[996]: [system] Activating via systemd: service name='org.freedesktop.PackageKit' unit='packagekit.service'
Dec 07 23:36:26 linux-shpr PackageKit[2165]: daemon start
Dec 07 23:36:26 linux-shpr dbus[996]: [system] Successfully activated service 'org.freedesktop.PackageKit'
Dec 07 23:36:27 linux-shpr PackageKit[2165]: uid 1000 is trying to obtain org.freedesktop.packagekit.system-sources-refresh auth (only_trusted:0)
Dec 07 23:36:27 linux-shpr PackageKit[2165]: uid 1000 obtained auth for org.freedesktop.packagekit.system-sources-refresh
Dec 07 23:36:27 linux-shpr PackageKit[2165]: uid 1000 is trying to obtain org.freedesktop.packagekit.system-sources-refresh auth (only_trusted:0)
Dec 07 23:36:27 linux-shpr PackageKit[2165]: uid 1000 obtained auth for org.freedesktop.packagekit.system-sources-refresh
Dec 07 23:36:58 linux-shpr PackageKit[2165]: refresh-cache transaction /1_eeacbeec from uid 1000 finished with success after 30901ms
Dec 07 23:36:58 linux-shpr PackageKit[2165]: refresh-cache transaction /2_adaaaade from uid 1000 finished with success after 18ms
Dec 07 23:36:59 linux-shpr PackageKit[2165]: get-updates transaction /3_eeedbddb from uid 1000 finished with success after 1051ms
Dec 07 23:37:16 linux-shpr PackageKit[2165]: daemon quit
Dec 07 23:37:16 linux-shpr packagekitd[2165]: (packagekitd:2165): GLib-CRITICAL **: Source ID 6 was not found when attempting to remove it
Dec 07 23:40:04 linux-shpr login[2384]: pam_unix(login:session): session opened for user root by LOGIN(uid=0)
Dec 07 23:40:04 linux-shpr systemd[2393]: pam_unix(systemd-user:session): session opened for user root by (uid=0)
Dec 07 23:40:04 linux-shpr login[2384]: ROOT LOGIN ON tty2
Ctl-Esc and alt-F2 did not work for me. I did not know about C-A-backspace. I'd like to know if there are some other commands I can try if this happens to me again.

At the time of the crash I had several programs open in different windows, including firefox, dolphin, vBox, and liboffice spreadsheets.

The desktop has not crashed on me yet today and so at this point it is not repeatable.