P: Desktop: Syncing Issues when Originals are stored on a NAS

I am also having the same issue; have there been any updates on a path to resolution?

Update 2: After over 5 hours of processing the Lightroom has synchronized the catalog. Took a bit of time and bandwidth for no reason but luckily all works afterwards. Hope this does not happen too often but to me it is clearly a bug in Lightroom software...

Update: I was not able to make it work in any other way than resetting the local storage to default. After that the Lightroom has shown a message that the folder in which I've had originals is not accessible (not correct - access worked ok), I've removed this folder on that message and reconfigured it again. Lightroom is now synchronizing all photos again (but seems it is not copying them over again). Let's see how it goes (55k photos to go, 5k done).

And here come new problems. After some issue with accessing shared folder (not sure what it was, I had to remove and map again the network drive). Lightroom was showing message that the folder is not accessible. After fixing it Lightroom now is checking photos with below dialog box and nothing moves even after hour of waiting. How to fix that?
NAS folder works all ok, no degradation in performance whatsoever. Original photos are where they were. Never had such issues with Lightroom Classic. Was able to disconnect network drive, move it around etc. all was updating super fast.

This is the conclusion I came to, too. 

This doesn't sound related to the thread.  It sounds like you have nine images that are stuck.  Check for assets in your Deleted Items first and see if you can clear anything there. 

Next, go to https://lightroom.adobe.com and see if you have any images in the special album called Sync Errors (upper left):  The black thumbnails, if any, will advise you on steps to take from there. 

Rikk, there seems to be variations of a basic problem, and I would like confirmation that my problem is the same.  I work on a PC (Windows 10) and my local storage for Lightroom Desktop is a Synology NAS.  I have about 35K items in Lightroom.  Most are jpg or CR2 photos, TIF scanned photos/35mm slides, and around 400 videos.  After loading new pictures into Lightroom, they sync very quickly (100 new images are processed in less than 10 to 15 minutes). My problem is syncing always fails to advance below 9 images.  This has been occurring ever since I migrated my photos from Lightroom Classic about 2 months ago.  When I filter on SyncStatus = Syncing, I get the "Oh no! A black hole." screen, but the Cloud status indicates "Syncing 9 photos." I would like to know if this is the same problem that is being worked by Adobe support or do I have to do something different to have someone work on it.  Thanks for your attention.

I'm facing the same problem more than 1 year now. And this is not a problem related to synology NAS as I've had this issue with my previous NAS that was just a Linux computer.

Is iSCSI still the only way to get Lightroom running with Catalina?

Thank you.