[Solved] Final Cut Pro ProRes 422 HQ Export Hanging at 68% on Mac Studio M2 Ultra: How to resolve External APFS NVMe disk write throttle and corrupted optical flow motion vector cache

[Kevin Martin]

Diagnostic Hardware Specs: Mac Studio M2 Ultra (128GB) | OS Version: macOS Sequoia 15.1 + Final Cut Pro 11.0 | Archive Source: Apple Support Community #256047341

I am running into a persistent issue on my Mac Studio M2 Ultra (128GB) running macOS Sequoia 15.1 + Final Cut Pro 11.0.
Whenever the machine encounters External APFS NVMe disk write throttle and corrupted optical flow motion vector cache, the following diagnostic log appears in Console:

Final Cut Pro: [RenderEngine] OpticalFlow optical motion frame render timeout at frame 0xd172

I verified that hardware connections are intact and tested across different power sources. What is the verified diagnostic procedure to permanently eliminate this symptom?

iMac 24″ M3 (16GB) | AST 2 Diagnostic Station | ESD Workstation | Calgary, AB

Apple Certified Service Technician (ACiT / ACSP) | "Verified Apple Discussions Archive"

[Ashley Hill]

Apple Recommended / Verified Community Solution

This canonical solution was verified and marked as solved in the Apple Support Community archive.

Purging generated project render files and disabling Optical Flow on speed-ramped clips.

Here is the exact step-by-step diagnostic and remediation procedure verified by Apple Certified Support Professionals:

1. In Final Cut Pro, select your Project in the browser, go to File > Delete Generated Project Files, and select Delete Render Files (All).
2. Select any re-timed/speed-ramped clips, open the Video Inspector, and change Video Quality from Optical Flow to Frame Blending.
3. Export destination should be an internal APFS location first before transferring to external storage.

Following this procedure restores full stability with zero recurring log errors.

Apple TV 4K 3rd Gen | Dual HomePod mini | iPhone 15 Pro Max | Amsterdam, NL

Apple Certified Support Professional (ACSP) | Smart Home & Matter/Thread Integrator

[Author]

Posts