Same on "Kubuntu 16.04.2 LTS" with 4.8.0-52-generic kernel.
After automatic switching access points the process "plasmashell --shut-up" generates 100% CPU load.
In my case, it is related to the Skype 4.3.0.37 application.
As soon as I kill the Skype tray icon, the "plasmashell --shut-up" vanishes and the CPU load goes back to normal.
Same on "Kubuntu 16.04.2 LTS" with 4.8.0-52-generic kernel.
After automatic switching access points the process "plasmashell --shut-up" generates 100% CPU load.
In my case, it is related to the Skype 4.3.0.37 application.
As soon as I kill the Skype tray icon, the "plasmashell --shut-up" vanishes and the CPU load goes back to normal.