Help! Can not modify Red Raw settings from FCPX - keeps saying "Final Cut Pro must complete other tasks"

Please confirm disk format as either MacOS Extended or APFS.

If a new library with a RED file work fine, it could be the previous library and/or timeline are corrupt. You could try exporting an XML of the previous timeline and importing into the new library.

X2Pro can be used for output to AAF.

Send Feedback to Apple to improve FCP's audio capabilities. Final Cut Pro->Provide Final Cut Pro Feedback...  or use this link Feedback - Final Cut Pro - Apple

I don't use RED media but I believe they require a plugin. You have the most up-to-date version?

Please post screen shots of what you're seeing.

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FCP works fine with REDRAW media and I frequently edit that. However it is very compute-intensive. In general a top-spec 2019 i9 MacBook Pro 16 is not fast enough for 8k/23.98 R3D. An M1 Max MacBook Pro or above is fast enough.

This can be exacerbated by using a timeline and multiple clips with effects. That could explain why one test clip works but your timeline does not.

If you are not on an M1 Max or above, AND have background rendering enabled, it can take lots of time to crank through R3D clips on the timeline. During that period certain actions will be disabled, maybe such as changing RED RAW settings. I suggest turning off background rendering in FCP preferences.

If you are not on an M1 Max or above and are having performance problems editing RED RAW material, that is not an FCP issue. Resolve is the same.

I've been having that same issue for years now. It's seemingly random. Some clips it works fine, others it'll give me the "must complete other tasks" pop up. I've tested it with a variety of settings but I've landed that it's a random occurrence.

Do you have access to Resolve? For all RED raw material, my workaround is still cutting in FCP X, but transcoding/optimizing all media in Resolve and then importing into FCP.

Difficult problem. Not seeing it on my system.

What drives are you using and how are they formatted? Try creating a new admin user and see if it has the same issue.