The following entries are missing in xcb keyboard table:

XK_ISO_Group_Shift
XK_ISO_Group_Latch
XK_ISO_Group_Lock
XK_ISO_Next_Group  
XK_ISO_Next_Group_Lock
XK_ISO_Prev_Group  
XK_ISO_Prev_Group_Lock
XK_ISO_First_Group 
XK_ISO_First_Group_Lock
XK_ISO_Last_Group  
XK_ISO_Last_Group_Lock

So whenever one of these is send via xcb key press or releas event an empty Qt key event is generated.

This again could result in a partial match inside QShortcutMap (It actually does inside QtCreator). If we trigger a partial match the next keystroke is consumed and will not be send to the correct receiver.

Also see QTCREATORBUG-9589 for additional information.