I am having the same issue. I cleaned up all my old bookmarks in my Chrome browser and tried to use the sync tool to overwrite the server data for the bookmarks. After about 3 minutes, I received an error stating that the sync failed. I try many times to repeat this process and received the same results.
go to https://everhelper.me/client/
and clean your database. then try to sync again.
Customer support service by UserEcho