P: Export as Catalog fails to external exFAT SSDs on macOS Tahoe 26.5.2 (works to internal APFS SSD)
- July 25, 2026
- 5 replies
- 65 views
Lightroom Classic Version
15.4.1
macOS
Tahoe 26.5.2
Hardware
MacBook Pro (Apple Silicon)
Description
Export as Catalog consistently fails when the destination is an external exFAT SSD.
After several minutes Lightroom displays:
“An unknown error occurred while exporting the catalog.”
The partially created export folder is then deleted.
The identical export succeeds immediately when the destination is the internal APFS SSD.
Reproduction
- Open any Lightroom catalog.
- Choose File → Export as Catalog.
- Select an external exFAT SSD.
- Export with or without negatives.
- Wait.
- Lightroom reports “Unknown error occurred while exporting the catalog.”
Expected
Catalog exports successfully.
Actual
Generic error.
Export folder deleted.
Reproduces on
- Samsung T9 (exFAT)
- SanDisk Extreme SSD (exFAT)
Does NOT reproduce when destination is
Internal APFS SSD.
The same catalog (approximately 415 GB including negatives) exports successfully to the internal APFS SSD in a few seconds. The resulting exported folder can then be copied to the same external exFAT SSD with Finder without error. Only direct Export as Catalog to the external SSD fails.
Additional observations
- Reproduces with:
- 4,000-photo catalog
- one-photo catalog
- brand-new empty catalog
- Catalog integrity verified.
- Disk Utility First Aid clean.
- Finder copies hundreds of GB to the same SSDs successfully.
- Different USB-C cable tested.
- Rebooted.
- Exporting without negatives also fails.
- Exporting to the internal SSD succeeds.
- The successfully exported catalog can then be copied to the same external SSD using Finder without issue.
- The workflow worked reliably for months before upgrading to macOS Tahoe and/or Lightroom Classic 15.4.1.
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