FCPX occasionally becomes unresponsive switching between timelines

Have you tried resetting FCP preferences? Whenever FCP crashes, is Force Quit, or starts acting strangely an easy thing to try is deleting FCP preferences. Hold Option and Command while launching FCP and choose Delete Preferences. It will open the default Untitled library. Re-open the library you were working on, set the Preferences back to the way you like them (disable background rendering, reset Import to Leave Files in Place, etc.) and see if the issue has been resolved.

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In the FCP 10.7 Manual I found the keyboard shortcuts are command-[ and command-]

I'm currently on the latest and greatest.

Does the latest version mean 10.7? Latest doesn't necessarily mean best. Because 10.6.10 is currently the most stable version.

It becomes unstable if you keep multiple projects open all the time or if program garbage accumulates. Additionally, running other apps will increase the load on your PC.

Always. They’re actually drop down menus, so if you’ve opened a number of projects you can select the one to open. Clicking just goes back to the previous project.

I am distraught thinking of all those seconds I have wasted over the past 12.5 years double-clicking the projects in the Browser!

I have just discovered that it's the central (downward facing arrow) that produces the dropdown menu.

Try this

That's on either of the end brackets. It's a little confusing what appears where. If you're in one of the "middle" projects, earlier ones will be on the left bracket, and ones opened later will be in the right bracket.

How many projects do you usually have open at a time? It’s not something I’ve seen but I rarely have more than two projects open, leaving aside multicams and compounds.

the program doesn't respond to any clicks or keypresses and a force quit becomes necessary.

What version of FCP?

I have been using FCP X since its inception and have never noticed those 2 arrows (Go Back and Forward in Timeline History).

How long have they been there . . . always? 😢

Got it. Thanks.

For some reason it wasn't working before.