SUMMARY
Error opening the disk in ReliableDR Replication jobs
ISSUE
This problem occurs rarely on ReliableDR Replication jobs and is visible on debug view window.
During the test could happen that some VMs internal files are locked for exclusive use, so the open or read attempts will fail.

ReliableDR retries the operation before giving up on the replication job, sometimes succeeding other times failing.
The number of retries is established on settings window.

If the problem persists there is still a couple of things to try:
- It could be related with the ReliableDR connectivity requirements:
ReliableDR also needs DNS resolution of all ESX hosts (source/primary) involved in the replication if they are added to the vCenter via the hostname.
- Enter ReliableDR server and check VDDK logs at C:\WINDOWS\Temp\vmware-SYSTEM, if you see this error:
Error: Not licensed to use this function. Error 16064 at 2357
The problem is that vCenter user has not permissions at vCenter top level, see this VMware kbase article for more information: