When I edit a participant, a new subwindow opens (it's not really a window, but I looks like one, and the original website turns grey and unresponsive). That window is too unstable in the sense that an accidental click outside the window, or a stroke on ESC results in the following situation: the edit window disappears and the original page (the participant list) remains grey and unresponsive. Only refreshing brings the page back to life. That's a bit annoying.