Created attachment 106292 [details] Screenshot As shown in the screenshot excerpt containing the bottom 76 pixels of my desktop, the panel is not drawn completely but shows 5 pixels of the background image instead at the very bottom. Playing around with the panel settings did not seem to be able to correct this issue. I'm using plasma-workspace 4:5.10.2-0ubuntu1~ubuntu17.04~ppa1 from http://ppa.launchpad.net/kubuntu-ppa/backports/ubuntu .
Does it happen with all Plasma themes? You can change them with systemsettings5 > Workspace Theme > Desktop Theme. Additionally, try Alt+Shift+F12 to disable compositing. It is possible that your video drivers expose this bug.
(In reply to Christoph Feck from comment #1) > Does it happen with all Plasma themes? You can change them with > systemsettings5 > Workspace Theme > Desktop Theme. No. > Additionally, try Alt+Shift+F12 to disable compositing. It is possible that > your video drivers expose this bug. Alt-Shift-F12 had no effect. But, interestingly, playing with the compositor settings (System settings -> Hardware -> Display and Monitor -> Compositor) revealed that KDE decided at some point in the past that OpenGL detection on my machine is prone to crash the system and disabled it. Once I clicked "re-enable OpenGL detection", the panel looked fine again. Thank you for the hint! For the records, I use Intel's i965-va-driver 1.8.0-0intel1 on an "HD Graphics 530" (Lenovo ThinkPad T460p, i7-6700HQ).