This bug happen in KDE NEON Bionic. https://bugs.launchpad.net/ubuntu/+source/plasma-workspace/+bug/1684240 This bug have more one year and now in bionic. When will it fix?
Looks like a video driver issue? Not really plasma's nor neon's realm.
No, this is a bug of KDE NEON. This not happen in other distros like Kubuntu, Manjaro, etc, only KDE NEON.
*** This bug has been marked as a duplicate of bug 382812 ***