TOPIC:

Running new M1-Max MBP and FCP v10.6.1 freshly installed.

Even though I checked and the keyboard definition for the Space-Bar is Stop/Play, it doesn't work.
Instead it steps backward a frame at a time!

Any ideas?

Go to System Preferences, Keyboards, Shortcuts, click "Restore Defaults".
System shortcuts override application shortcuts, I've seen them interfere in weird ways, too.

Also, hold cmd+opt while launching FCP and delete preference files. That could help maybe.

Thanks for your suggestions, however the problem was traced to an Accessibility option: Keyboard/Enable full keyboard access - was ticked. Unticking fixed the problem. It IS a rather ambiguous feature.

Anyway, in the end I decided to reformat my SDD and install everything one at a time. Takes time, but I think it was worth it in the long run to avoid problems carried over from previous installs.