I experienced this bug on both my laptops (both with Nvidia 9xx series GPUs) with KDE Neon (developer stable), but not on my desktop PC. All are running the latest proprietary Nvidia 390 drivers.
I observed today that the problem only occurs when the Nvidia GPU is in use (sudo prime-select nvidia). The problem disappears if I switch to the Intel GPU (sudo prime-select intel).
Interestingly, the problem does not occur on my laptops when running Kubuntu 17.10, regardless of the GPU in use.
I experienced this bug on both my laptops (both with Nvidia 9xx series GPUs) with KDE Neon (developer stable), but not on my desktop PC. All are running the latest proprietary Nvidia 390 drivers.
I observed today that the problem only occurs when the Nvidia GPU is in use (sudo prime-select nvidia). The problem disappears if I switch to the Intel GPU (sudo prime-select intel).
Interestingly, the problem does not occur on my laptops when running Kubuntu 17.10, regardless of the GPU in use.