Troubleshooting Steps:
Transcode the 100fps Clips:
Before importing into FCP 11, try transcoding the 100fps clips to a different codec, such as ProRes 422.
Use either Apple Compressor or another video transcoding tool.
This can help ensure that FCP 11 can handle the codec.
Create a New FCP 11 Library:
Avoid using the legacy library from FCP 10.8.1.
Create a completely new library in FCP 11 and import the 100fps clips.
This will remove any potential for legacy settings to cause issues.
Optimize or Create Proxy Media:
In FCP 11, try generating optimized or proxy media for the 100fps clips.
This can reduce the processing load on your Mac and improve playback performance.
Check Project Settings:
Ensure your FCP 11 project settings are appropriate for the 100fps footage.
Verify the frame rate, resolution, and codec settings.
Update FCP 11 and macOS:
Double-check that you have the latest versions of FCP 11 and macOS Sequoia.
Apple often releases updates that address bugs and improve compatibility.
Test Different GH6 Recording Settings:
If possible, try recording new test clips with different recording settings on your GH6.
Experiment with different codecs, bit rates, and color profiles.
Check External Drive:
If the video files are stored on an external drive, make sure that the drive has enough speed to provide the video files to the computer in a timely manner.
Playback Settings:
In FCP, ensure playback quality is set to "Better Performance" instead of "Better Quality" to reduce the processing load.
Report to Apple:
Since you've replicated the issue across multiple M-series Macs, it's likely a software bug.
Report the issue to Apple Support through their feedback channels.
Why FCP 10 Works:
FCP 10.8.1 might have a different way of handling HFR footage, or it might have specific optimizations for the GH6's output.
Older versions of software often have different code bases that handle things in very different ways.
By systematically working through these troubleshooting steps, you should be able to narrow down the cause of the problem and find a solution.
