Missing Plugin error whilst using multi-cam clips

You have CleanMyMac installed, which can break the OS and cause problems for professional applications. Start by completely uninstalling. It's possible it's damaged the OS and you'll need to reinstall Sonoma.

You have Google's autoupdating software installed which can break the video toolbox. To completely remove Chrome and all the cruft Google installs, follow the instructions at https://chromeisbad.com then reinstall FCP from the App Store.

Your SanDisk SSD is full. You want a minimum of 15% free space on drives.

You likely don't need to optimize the footage if it's playing back from the SSD, so turn off Create Optimized footage in Settings. Then select the library in the browser and use File->Delete Generated Library media and remove everything. If you do in fact need them, you can always easily regenerate.

Try trashing your settings. Hold Opt-Cmd as you launch the application.

That's very basic information. Please give complete specs from MediaInfo or Invisor.

Can you reproduce this in another library? Does the media outside of the multicam show this problem?

Two in one day

  [Running] com.macpaw.CleanMyMac4.Agent.plist 

This has likely damaged your system. You may need to reinstall the OS and reinstall FCP.

Is this happening with just the multicam clips?

If you double-click on a multicam to open it in the Angle Editor, do the different angles play?

If you make a new library, and create a multicam clip there, does it have the same problem?

Please give the complete specs of the media from MediaInfo.

Does this appear on all clips? Does this appear on the browser clips? Have you applied any effects?

15% minimum on SYSTEM drive, secondary drives are not used the same way, it doesn't matter on those.

Please run Etrecheck and post its full report here. Use the "additional text" button and paste the report into the text box.

Thank you very much for reporting back.

Right! Good catch Ben.