Lightroom Classic: Export doesn't add newly created DNG files to catalog and prevents Lightroom from quitting

A Preference File will survive a Lightroom uninstall/reinstall and sometimes weird behavior is corrected/cured by resetting the preferences. 

Reset Procedure:

1. Close Lightroom.
2. Hold down [Alt/Opt]+[Shift] while restarting Lightroom. 
3. Overwrite the Preferences when prompted by the dialog.
4. Close Lightroom.
5. Restart Lightroom.

Does the behavior continue after resetting the preferences or does it still freeze up at the same place?

Did as you asked, indeed lost my preferences and behavior is exactly the same as described: no DNG's in catalog, no stacking, quitting Lightroom only possible by force quit.

I just did a test with a single Canon .CR2 and then a group of 6 Canon .CR2s. In both cases, the Export operation finished, the files made it into the catalog, stacked with the original and Lightroom appears to be functioning normally including a normal close of the program.  

Let's get some information from you: 

Operating System Version Number:
Lightroom Version/Build (Can be found at Help>System Info...):
Location of originals (local drive, external, type): 
Approximate number of photos in your attempt: 

Does it work with a single photo ARW file? 

Note: this is a fairly elaborate procedure and takes some time to complete. On a large number of photos it could seem like your system is unresponsive - even though it is attempting to complete the import/stack operation. 

Operating System Version Number: macOS 10.13.4
Lightroom Version/Build: 7.3 [ 1164630 ]
Location of originals (local drive, external, type): originals are at local drive (iMac internal SSD)
Approximate number of photos in your attempt: 5

Tried the same procedure with a single ARW file located on local drive, exactly the same behavior. Retried with a single ARW file that is located on a NAS disk, connected with afp -> same behavior.

Ad,

I grabbed an ARW file to test and my result was the same. I am also using 10.13.4 and the 7.3 build you've noted above. I also am working off the MBP internal SSD drive.  Since we are seeing different results and since a preference file reset did not help out, my recommendation is to perform an uninstall of Lightroom and a reinstall from a fresh download.  Here are the steps:

1. Restart your computer.
2. Without opening any other software, use the Adobe Creative Cloud app to perform an uninstall of Lightroom Classic CC 7.3. 
3. When complete, restart your computer a second time. 
4. Without opening any other software first, use the Adobe Creative Cloud app to install Lightroom again.
5. Restart a third time (probably not necessary but a good troubleshooting step).
6. Launch Lightroom and attempt your Export to DNG - Add to Catalog - Stack operation. 

Success? Still the same behavior? 

An uninstall/reinstall is different than just updating from a previous version to 7.3 and even though the problem may have been present for several versions on your machine, this should eliminate a previous install issue that may have propagated forward. 

Let me know how it goes. 

Hi Rikk, thanks, I performed the uninstall/install process you recommended and alas, the faulty behavior persists, exactly the same. I tried it with one ARW file.

I tried a few other things as well:

• Make a new export preset with the same settings -> no difference
• Do the export from an ARW file in a folder that is not synchronized with Dropbox, as opposed to my regular photo locations -> no difference
• Different ARW files (from A7 and A7R2, compressed and uncompressed, and Panasonic RW2 file from GH2) -> no difference

To be sure, my iMac uses the new APFS file system, maybe that's different from your configuration.

Discovered just now that the stacking option causes the problem. Once that option is disabled, the export functions as expected: the DNG file is created and added to the catalog. Doesn't matter if "Above Original" or "Below Original" is selected.

That is an interesting detail, Ad.  

If you are willing and only as an experiment, could you create a blank catalog for testing, drop a few images into it and see if the newly created catalog can accomplish with stacking?

No problem. Made a new catalog and imported 5 images into a folder unrelated to the old catalog -> exactly the same behavior: works well without stacking, same problems with stacking.

As I am not able to duplicate what you are seeing, Ad, I am going to recommend using the workaround of not-stacking on export for now. Until I (or someone else) can reproduce or we can get a precise set of instructions, I don't have any more recommendations. I will continue to watch the thread and hopefully something will appear that sheds some light on this.