There is a very strange graphical artifact when there are unread notifications.
https://imgur.com/sAGmUW6
https://imgur.com/X0Ip1Zr

You could see this black line staying there. I was thinking it's some kind of hardware issue (my GPU or something) but after clearing the notifications this black line disappears.

My specs:
Operating System: Kubuntu 19.10
KDE Plasma Version: 5.16.5
KDE Frameworks Version: 5.62.0
Qt Version: 5.12.4
Kernel Version: 5.3.0-42-generic
OS Type: 64-bit
Processors: 12 × AMD Ryzen 5 1600X Six-Core Processor
Memory: 15,7 GiB of RAM
GPU: NVIDIA GeForce GTX 1060 3GB
Theme: Breeze Dark [KDE], Breeze [GTK2/3]
Icons: la-capitaine-icon-theme [KDE], la-capitaine-icon-theme [GTK2/3]

I guess you wanted to say "does NOT disappear after clearing the notifications", right?

Mamarok wrote:I guess you wanted to say "does NOT disappear after clearing the notifications", right?

No.
It looks like that this glitch occur only while there is an unread notification. It doesn't occur all the time, so I can't simulate it. I can say for sure that when I clear the notifications, this black line (which is staying over every other window and application) disappear.

I'm using Ubuntu 18.04 on my laptop and I didn't see this glitch there. But the hardware is different so I can't say that's because of Kubuntu (KDE) version.