Anyone using Plasma 5 knows that system tray is a mess. Icons go missing. They overlap. Random icons will show up. All sort of problem. I often kill plasmashell and then restart it. It is a two step process. We can use SIGSEGV to kill plasmashell and have it automatically restarted. The only caveat is that it will trigger DrKonqi. It is still better than having to run two commands.
killall -s SIGSEGV plasmashell
Benjamin Cane has an excellent article on all sort of kill options one can use in Linux.