Shared directories are not backuped by script

My Lan server works as nextcloud client for a nextcloud server located at my customer location. Sync works well both directions.
I use a batch file to make backups on clients hard disks over LAN (Lan server runs windows Server 2012 and network clients run Win 7 x64).

The backup script executes an instruction like this:

xcopy \server\folder… D:\backup\floder… /Y /E /R /K

After Nextcloud client installation on my Lan Server the batch simply ignores the directories subjected to sync (even if the nextcloud client is not running), while it copies other directories as usual. I can still copy “nextcloud” dir from the server to the client by Windows Explorer.