The message
Cannot perform stat(): ([3] The system cannot find the path specified
means that, after the Treewalk, a file has been deleted. However, the IDB is in Hot Backup mode, which means essentially, the filea are locked, so I would never expect to see this message during a IDB backup
Are you backing up the IDB as part of a file system backup? This is not a good idea, the IDB should have its own backup, and, ideally, be run when there is nothing else running
If this is not the case, first run
omnidbutil -extendinfo
so, we can see if the DCBF (Data Catalog Binary Files) is in a different directory, then, pick a time when there is nothing else running, stop DP to make a copy of 'db40', restart DP, and run
omnidbutil -remap_dcdir