I am sure that the problem is not solved. My version of plama-workspace is : dpkg -l|grep plasma-workspace
The problem CPU >100% appears often when i open and click to the icon Firefox on the taskbarRecently I have started plamashell in Konsole and i received plenty error messages when CPU grows more 100% the last error message received is : *QXcbConnection: XCB error: 2 (BadValue), sequence: 36336, resource id: 71303772, major code: 142 (Unknown), minor code: 3* no more messages and top give CPU > 100% When the problem arrived i kill the process plasmashell and i restart plasmashell. I don't know if this error message can help you to solve thr problem
