Unable to access file [unspecified filename] since it is locked

VMware holds a lock on the snapshot file while it is being consolidated. If there is an issue during this process, it is possible for further snapshots to be unable to consolidate, causing removal failures. You receive warnings that the snapshot removal process failed because '<unspecified filename>' is locked.

There are two common causes are:

1. The request to have disks released from a Veeam Backup Proxy at the job run was not processed by the vSphere environment, resulting in a condition called "Stuck hotadded disks."
2. The ESXi host is holding a lock on the specified snapshot.

If ESXi host file locks occurs frequently, it is advisable to check the network connection between Veeam and the source host, as well as the overall load on the source host at the time the backup typically finishes.