Incorrect synchronization

We had an extremely critical situation with the restored NextCloud file storage - after users connected to the NextCloud server from backups, it turned out that during the first synchronization, all changes made by users on their local computers during the entire last week were reset and all these new files were deleted - the storage returned to the form it had before the storage system crash. That is, reverse synchronization occurred and not newly created and modified files (with creation dates throughout the last week) were recognized as relevant, but old files and folders that were relevant at the time the storage system crashed on October 10th.

How could this happen?
If it is possible to disable this “reverse” synchronization from the cloud to workstations?