When I press the spacebar in Healing Brush mode, I can see the cursor flashing to a hand to a microsecond and then back to brush immediately after. Here's a quick video of the issue.
I've tried using an app called ShortcutDetective to check if there's any app generating a conflict in terms of hot keys and I couldn't see anything.
Holding spacebar and then holding ⌥ starts a scissor icon/tool that I've never seen before.
macOS 12.2.1 (Monterey)
Lightroom CC Version 5.3