P: Synchronize Folder hangs

I had the same problem. Tried to synchronize a folder and it crashed Lightroom without showing the thumbnail image. Found a workaround that solved the problem for me. With the thought that maybe something got corrupted in the lightroom file system I did the following all within the Lightroom program:

1. Created a new folder. (I renamed the old folder so I could keep the previous name on my new folder)

2. Moved all the images from the old folder to the new folder. This was about 3,700 images.

3. Then did a synchronize on the original folder and I was able to import the single missing file successfully.

4. Finally, copied the new file into my new folder and removed the old folder.

A big thank you to Rikk Flohr. I had a problem where the "Synchronise Folder" function would cause Lightroom Classic to hang which was very irritating. I came across Rikk's suggestion the reset the Preferences and "bingo" problem has been solved.

More details about this persistent issue...

I had a folder with about 3000 images. The problem appeared after I added the last few hundreds. I split the folder into multiple subfolders, each one containing no more than 600-700 images (same images, no change). The problem disappeared.

1. The problem is not tied to any technical issue with one of these images but rather to the number of images being processed (that is, compared).

2. For each synchronization, I only added about 20-30 images to the initial folder. All the images already present had been already processed and their preview was present. So, it shouldn't be a memory problem since only a few image previews have to be generated. And I have a lot of memory available on my system.

Hmm! Looks like a stack overflow problem. I guess that LR has to compare the new and already present images in order to detect duplicates and files of different types having the same names. I don't know how the comparison is being made but since LR crashes when doing this, I suspect a bug in the image list management.

Well, now back to my old obsession about LUA (the infamous language being used to develop the LR UI). I doubt that LUA is very appropriate for managing big lists the classical way by dynamically allocating memory for each item. I suspect that pre-dimensioned arrays are used to do this. And under certain circumstances, these arrays are probably too small and the code is not checking this. Otherwise I don't see why the synchronization process fails only when the number of images exceeds a certain limit (which appears to vary a lot depending on the user's system).

Just a guess.

I have excactly the same problem (Windows 10, LR 11.5).

It never happened before, and now after several successful synchronize with show import dialog, it happened suddenly. Tried to restart LR, Windows, but now I can only synhronize without the show import dialog. All was ok as long as the folder had less than approx. 2000 files.

Bernard

resetting preferences didn't work for me

win 10

lightroom classic 10.4

using folder on external USB drive

Same problem here on MacOS. This is extremely frustrating.

My culprit was android phone connected to PC via usb. When I disconnected it, import dialog and sync folder started working again.

Confirmed. Unfortunately. Very annoying bug.

Still not fixed in V10.11 

Problem not fixed in version 10.