Lightroom Desktop silently fails to export 13,000 originals; 5,500 succeeds

I am using Lightroom Desktop (cloud-based) on macOS 26.6 (Apple silicon).

Goal
Create a local backup of the original RAW files for approximately 13,000 cloud photos.

Steps to reproduce
1. Select approximately 13,000 photos in Lightroom Desktop.
2. Choose Export.
3. Select Original (the RAW originals) as the file type.
4. Choose the destination and start the export.

Expected result
The export starts and Lightroom shows visible progress. If this number of files is not supported, Lightroom should show a clear limit or error message.

Actual result
After clicking Export, Lightroom becomes silent. No export progress appears, no error is shown, and the process seems to be aborted.

Control test
I reduced the selection to approximately 5,500 photos and repeated the export with the same settings. That export succeeds. This suggests a size-related limit or failure somewhere between 5,500 and 13,000 files. I could not find a documented maximum for Lightroom Desktop exports.

Impact
I cannot reliably create a complete local backup of my cloud originals. The silent failure also makes it unclear whether the backup has started or completed.

Please confirm whether there is a supported maximum number of files per export and improve the progress/error handling for large exports.