Panorama merge always hangs at the background tasks "Assembling panorama" and "Saving metadata".

Lightroom Classic version: latest (Creative Cloud, fully updated) Version 15.1

OS: Windows 11

Camera files: Fujifilm X-H2 (RAW and DNG)

Problem:

Panorama merge always hangs at the background tasks

"Assembling panorama" and "Saving metadata".

The panorama DNG is created successfully and appears in the catalog,

but the background tasks never finish and block Lightroom.

After this happens, no further panorama merges are possible

until Lightroom is restarted.

Deleting the tasks manually does not help.

What I already tried (no success):

- GPU disabled

- New catalog

- Catalog optimized

- RAW converted to DNG and re-imported

- XMP auto write disabled

- Firewall and antivirus disabled

- Files stored on local SSD

- Preferences reset

Reproducibility:

100% reproducible.

I can always create exactly one panorama after starting Lightroom.

The second merge always hangs.

This is a serious workflow blocker.