The error message "Failed to copy files" often appears in the middle of the backup

[chansonsky]

Operating system: WIndows Server 2012 R2
Backup file size: about 1.42T
Number of files: about 2,000,000
Number of folders: about 790,000

1. Backup method: Incremental backup (creating a single backup with a timestamp)
Backup target path: local
Backup Results: Sometimes the backup completes normally. Sometimes during the backup, it prompts that the file cannot be copied, which causes the backup of some files to fail.

2. Backup method: incremental backup (mirror task)
Backup destination path: shared folder on other computers in the LAN
Backup result: often during the backup, it prompts that the file cannot be copied, and it also prompts "the original directory does not exist", delete the file just backed up to the shared folder of other computers in the LAN.

When using "Cobian Backup 11" to back up before, it has been relatively stable, and there is no error message. Later, when it was replaced with "Cobian Reflector", the WIndows operating system was also updated.
I don't know if this is because the number of source files is too large and the backup is abnormal? Or is it because of an incompatibility problem after the WIndows operating system is updated?