When user A opens a autocad file and the second user B that wants to open the same file, can open the file not as read-only as it has to be and doesn't get the notification that the file has been opened from user A. In this case user B can overwrite the file.
A similar Problem happens with sheet set files too. if user A creates a sheet file the and closes the manager, the second user can not edit the file anymore unless he makes a copy of this file or he puts it on an ntfs-sharing.
Our system is a virtualised UCS 3.2.1 errata67.
The first problem happens time to time and not all the time long, the second problem is permanent on a samba sharing.