Timeline export failures will happen on FCP 10.6.5 (and likely earlier versions), starting with Ventura 13.4 on Apple Silicon, if the timeline export contains any Sony 100 fps or 120 fps 10-bit 4:2:2 XAVC-S (H264) clips. It happens regardless of timeline frame rate or export codec. Whether the 100/120 fps material is retimed makes no difference.
Failure modes include: high CPU slow export, or apparent success but no output file appears on disk, or output file is unreadable, or output file is readable but shows damaged frames. It does not happen on Intel. Also, it does not occur on Apple Silicon with 100/120 fps 10-bit 4:2:2 XAVC-HS (HEVC) clips or with 100/120 fps 8-bit 4:2:2 XAVC-S clips.
I have not tested H264 10-bit 4:2:2 100/120 fps from other camera codecs such as Canon, Fuji or Panasonic.
The exact failure mode can vary, but the failure itself is 100% consistent. Even a single clip of the XAVC-S 100/120 fps material in a timeline of other codecs or in a pure ProRes 422 timeline will cause export failure.
Existing properly-functioning FCP projects created on prior versions of MacOS will begin having this problem if the Apple Silicon machine is upgraded to Ventura 13.4. The problem cause is evidently MacOS not FCP.
The clips show in the Event Browser and timeline as black, audio plays but no video. However, it is not merely a playback problem within FCP; the export will fail or produce a damaged file.
Resolve Studio 18.1.4 has a similar problem on the same XAVC-S material starting with Ventura 13.4. Like FCP, it works OK on Intel. Premiere Pro 23.4.0 works OK with this material on Ventura 13.4 Apple Silicon.
Apple Pro Video Formats were unchanged for Ventura 13.4, still on version 2.2.4. Unknown if that is related.
Ventura 13.4 machines tested: M1 Ultra Mac Studio, M2 Pro Mac Mini
Ventura 13.3.1(a) machines tested: M1 Max MacBook Pro 16, 2017 iMac 27