P: (macos) Lightroom v9.6: JPG export fails "There was an unknown error" on specific Leica M11-P DNGs; same photos export fine from iPad

Five Leica M11-P DNGs fail to export from Lightroom Desktop on Mac every time, with "Some export operations had warnings or errors / There was an unknown error. (5)". Other M11-P DNGs from the same shoot (also with in-camera Content Credentials) export normally. The same five photos export fine from Lightroom on iPad.

Affected files: L1006491, L1006432, L1006409, L1006407, L1006478 (.DNG). Leica M11-P, Summilux-M 50 f/1.4 ASPH, Content Credentials enabled in camera. Info panel shows 6055 x 4541, 33.51 MB for L1006491. Edits were made in Lightroom on iPad.

Steps: Select the five photos > Export > JPG (Small or Full Size, 90%, Adobe RGB) > Export.

Expected: five JPGs.

Actual: "There was an unknown error. (5)". Fails every time, not intermittently.

Tried, no change:

- GPU on/off, app restart

- Smart Previews on/off

- Clear cache + restart

- Reset all edits

- Several different profiles

- Full Size instead of Small

- Apply Content Credentials on/off

- Edit in Photoshop (also fails)

Works:

- Export as Original (DNG) from Desktop

- JPG export from Lightroom on iPad

- Exporting the DNG from Lightroom on iPad, AirDropping it to the Mac and exporting JPG from Lightroom Desktop Local mode. So the Mac can render the image; the problem seems tied to the cloud asset / original file as stored. Re-adding to Cloud is blocked as a duplicate.

Environment: Lightroom 9.6 MAS arm64 [20260923-1659-a32d844], Camera Raw 18.7 [2743], macOS 27.0.1 (26A434), MacBook Pro M3 Max (Mac15,9), 128 GB RAM. Originals stored locally, cache at Maximum, ~498 GB free.

I can share an affected DNG privately with Adobe staff.