So, I started calibre-debug -g (sorry, should have done that before), and here's what the log says when I press "s":
QAction::eventFilter: Ambiguous shortcut overload: S
The GUI states that there is no collision with the "s" shortcut (and it definitely was not with the 2.x versions)
So, I started calibre-debug -g (sorry, should have done that before), and here's what the log says when I press "s": :eventFilter: Ambiguous shortcut overload: S
QAction:
The GUI states that there is no collision with the "s" shortcut (and it definitely was not with the 2.x versions)
Maybe that helps?