Comment 3 for bug 1266795

It might have something to do with the fact that that widget has completion popups. When the popup is active, key events have to be redirected from the popup to the line edit. However, the redirection is pretty simple, so I dont see where there could be a bug, see Line 191 onwards in https://github.com/kovidgoyal/calibre/blob/master/src/calibre/gui2/complete2.py