Unknown Error when trying to import another catalog May 2018

Hi all,

Posting this as a new discussion as I can't find the same issue elsewhere.

I have returned from a trip and want to merge the catalog on my travel laptop into the master catalog on my home PC.

At this point in time both devices are running Windows 10 (1803 Build 17134.48 upgraded last week) with LR Classic CC 7.3.1.

Both devices have catalogs on local C:\ drives and image files on data drives with plenty of free drive space (well over 100GB on each).

PC master catalog folder is ~2.5GB, Lightroom Catalog.lrcat is 167,580 KB.

Laptop catalog folder is ~1GB, Lightroom Catalog.lrcat 43,512KB.

After previous trips I have returned home and followed this procedure:

1. Copy all new (RAW/NEF) and developed images (JPG) from laptop to PC internal data disk (F:\ Drive)

2. Copy the laptop catalog to PC internal data disk (F:\ Drive)

3. Open LR on PC (with local catalog on C:\ Drive), select 'Import from another catalog...'

4. Select the required catalog on data disk (connect to drive directly, NOT via mapped drive)

5. Select 'Catalog Contents' - All Folders, 'New Photos - Add new photos to catalog without moving

6. Import new catalog into master PC and relink folders to new locations

7. Test all OK

This time I have followed the same procedure, but instead of importing the laptop catalog I get "Lightroom could not import this catalog due to an unknown error" after step 5.

I have retried with various ideas, but all result in the same error message.

Catalogs have been optimised, created a fresh laptop catalog, have replaced the master catalog from a copy, tried partial import rather than all folders, tried copy of laptop catalog on PC local C:\ Drive, all with the same result.

If I open the laptop catalog on it's own on the PC it works fine, links to the correct data location, shows all develop settings etc.

Even used PC  to open a local C:\ copy of laptop catalog, created a local backup, then reopened LR to try import from new backup - same error.

I have even re-installed LR on my PC, but it still won't import to the PC master catalog.

Also I tried to import my PC master catalog into the laptop catalog on the laptop - guess what? Same error.

Whatever way I can think of to merge these 2 catalogs the same error appears.

What now? I really don't want a situation where every future trip has to have it's own catalog.

Any other ideas? Is there another way to merge catalogs?

This has taken hours/days this week with no progress - getting very frustrated and don't have another support route to Adobe on my package.

Hope somebody can shed some light on this.