Bummer. In case the problem should reoccur you could try the following to help narrow down its cause: Check for chromium-browser threads with
ps -aux | grep chromium
and note down their PIDs. Stop the plugin and check again if there are still chromium-browser processes. There should not be any chromium-browser threads at this point, but if there are compare if their PIDs are the same as you have seen prior to stopping the plugin. Kill possibly still running chromium-browser processes with
sudo killall chromium-browser
and start the plugin. If the problem persists stop the plugin again, make sure no chromium-browser processes are running and then not only delete the content of /data/volumiokiosk as described above but also the directory “chromium” in ~/.config with
rm -rf ~/.config/chromium
before restarting the plugin.