[Reg] QWebEngine: Zoom requests are activated multiple times when executed from shortcut

I've augmented the 'minimal' WebEngine example to add 'zoom' keybindings (see attached). When I invoke the keybinding (with 'Command + ='), the window is zoomed multiple times (three times in my case).

Not sure if this is a more general issue with QShortcut bindings with QWebEngine (is something causing all kinds of QShortcut activations to be delivered multiple times?)