Back in November 2020, Dropbox started to crash frequently and help for the reported error suggested reinstalling Dropbox. My log notes for the re-installation noted that I had specified the location to be the same as before, E:\Dropbox. After the installation, Dropbox sync'd for a while and then reported it was up to date. Unfortunately, Dropbox had placed the Dropbox folder at its original location on my system drive C:. For the next two months, I edited thousands of photos in my E:\Dropbox folder. When I discovered this, I reinstalled Dropbox and this time managed to get it located correctly back to E:\Dropbox. However, after Dropbox Sync'd, E:\Dropbox now contained thousands of pairs of files, one with the filename as stored in the online Dropbox and the other edited version of the file renamed, adding "(Doug's conflicted copy 2021-01-17).
I restored my E:\Dropbox from a backup and deleted the online Dropbox folders, which were not shared. I then reinstalled Dropbox and waited while it sync'd. But I noticed that folders and files on my E:\Dropbox were being deleted and quit Dropbox to stop the damage. (I do have a backup made just prior to this that I can use to repair E:\Dropbox.)
I had naively thought that, since I had deleted the folder online, Dropbox would consider the folders in my E:\Dropbox to be new and upload them. Instead, it seems to have decided that, since I had deleted a folder by the same name, it should delete that folder on all linked computers. How do I make Dropbox recognize that an unshared folder that has been deleted online should not cause a new folder in the local Dropbox folder to get deleted?
Thanks, Lusil. That's what I eventually concluded over the weekend. On my local E:\Dropbox, I deletd the contents of any folder with conflicted files, reinstalled Dropbox and let it sync. Since then I have been copying backup files into those folders and adding any other backup folders that were missing. It is a long process since I am having to restore about 750GB, but it is going well. i'll flag this thread solved after I complete the restoration.