Hi Intenditore! can you please provide more infos:
Dual Monitor ?:
Graphic Card and driver version?
if possible a screen recording can also be very helpful to us.
Here its working as expected to me but im using one monitor only and its a notebook.
I will try to trigger it in my desktop on monday.
usually the space bar is sensitive to Powerslider, Timeline and Viewport
with active viewport it will toogle your between the lastest two tools.
with power slider or timeline it will play the timeline and stop the timeline.
You can also try to disable Mouse Move Activation in preferences and see how it behaves to you.
I hope you can trigger it again, solid reproduction steps are very helpful and they allow us to react quickly.