Final Cut Pro 12.3 Better Optical Flow fails silently on Intel Macs

FCP v12.3 Bug: Better (Optical Flow) completes analysis 100% but silently fails (choppy/stepping playback) on Intel Macs

Hello everyone,

I am running into a highly frustrating and specific rendering issue in Final Cut Pro v12.3 on an Intel Mac, specifically when trying to apply Better (Optical Flow) to native footage.

When I slow down a clip on my timeline and apply Optical Flow, the background task window (⌘9) successfully triggers, builds the frame cache, and completes the analysis all the way to 100%. The timeline shows no dotted render lines, indicating FCP believes the clip is fully processed and ready for playback.

However, during timeline playback—and even after a final project export (⌘E)—the optical flow is completely ignored by the rendering engine. The clip plays back with hard, choppy frame-duplication (stepping), acting exactly as if the Video Quality was left turned off or set to Fast (Floor).

I also have no Analysis folder in the library for me to delete manually to force reanalysis.

Is this a bug in the new update, at least for Intel machines?

3.3 GHz 12-Core Intel Xeon W

AMD Radeon Pro Vega II 32 GB

96 GB 2933 MHz DDR4

Tahoe - 26.6.2 (25G83)