The issue of Lightroom Classic freezing and crashing when syncing collections to lightroom.adobe.com was addressed in the list of bug fixes included in the new Lightroom Classic version 12.4. It did not help. I installed 12.4 this morning. I was able to sync a few collections and then it crashed. I cleared lightroom.adobe.com and removed All Synced Photographs and tried again. This time it crashed in a different spot. Sometimes it crashes when I am not syncing. I have had it crash upon importing files. I have had it crash after opening the program. I am totally baffled.
This has been going on since March 5th, 2023. I have been in contact with Adobe Technical Support numerous times and have had to explain the problem to a different person each time. I asked that the problem be escalated and they dumped and uploaded some log files. They were supposed to analyze the logs and get back to me. That didn't happen.
I have tried everything suggested to me by Adobe and in the forums. The Adobe techs have been into my system and messed things up a couple of times. Nothing has helped. I am frequently testing the integrity of my catalog and it passes the test each time so I know that my catalog is not corrupted.
Anyway, if you are still on an older version of Lightroom and having this problem, upgrading to 12.4 will probably not help.
By the way I am running Windows 11. Not sure if that has anything to do with this problem.