I was finding that while working with clips in the browser window in FCPX, using the space bar to start and stop playback, would invoke the reject clip option, which makes it disappear from the browser window. After trying to figure out why, I tried disabling KM and it resolved the problem. Turned KM back on, and the problem happened again. I have no FCPX or global macros which use the space bar, so how could this be happening? It means I have to turn off KM when I am working in Final Cut, which is a drag, of course.
You might take a look at the Keyboard Maestro Engine log immediately after the issue occurs in FCPX. From the KM Editor, open the menu Help > Open Logs Folder and then open the Engine.log file, and inspect the last few entries.
That provided the answer! I had downloaded a global macro from this site called “Autocorrect i”. It’s purpose is to automatically make i become capital I. That was being invoked by the space bar for some reason. So I disabled it and it solved the problem. I guess it works by typing i and space, but it’s written in such a way that it is not really clear.
Thank you for helping solve this.
Better yet, use the new Assistance window which helps solve exactly this sort of problem. Choose Help ➤ Assistance and click the Something unexpected is happening link.