I am so tired of seeing a folder containing several hundred images that I have worked to edit, and the edits just disappear. I don't know when this happens, or why. I have 32,000 images, so I can't constantly monitor every folder. I'm not changing anything, just updating when they become available, backing up the catalog when it says to do it. I'm using Windows 10 Pro on a Dell XPS17 laptop.
this has been happening to me also. i have LR classic 10.4 on an older iMac that can't be upgraded to the current version. i also have the current LR classic and LR reg on a newer laptop and on the phone. whenever the older version syncs to one of the newer versions it wipes out any edits that used gradient masks or brushes which is virtually all my edits. i think it's related to the upgrade and enhancements they made recently to gradients and masks and their incompatibility with older edits that used previous versions of the masks/brushes. i usually have snapshots of my final edits so can use them to get back what the edit should look like. have had to stop syncing between the cloud and my different LR versions on different devices to avoid this for the time being. not sure if your problem is a similar issue but it is troublesome to say the least.