Terminal window (lower part of the screen) cannot be enlarged



You see: there’s only 1 line visible now, and the arrows to enlarge the window are gone.
The only actions possible are hiding the window (by F6 or click on ‘X’), or enlarge it to fill the whole screen (by clicking the icon). I can cure this behaviour by refreshing the complete C9 IDE, but I don’t think that it is meant to be this way. Does someone know what to do about this?