VM guest can't be modified or removed from a protection group in Data Protection Manager

This article provides a solution for an error that occurs when you modify a protection group or remove a VM from a protection group.

Original product version:   System Center 2016 Data Protection Manager
Original KB number:   4018988

Symptoms

When you try to modify a protection group that contains Hyper-V Virtual Machine (VM) guests, or you try to remove a VM from a protection group, you receive an error message that resembles the following:

Removing Guest_Name failed:
Error 157: Guest_Name cannot be added to protection because it is already a member of a protection group.

Cause

This issue is due to duplicate entries in the DPM database. The duplicate entries may occur after a protected virtual machine is migrated from one Hyper-V cluster to a different Hyper-V cluster, and then that VM is re-protected on the new cluster.

Resolution

To fix this issue, contact Microsoft Support for help removing the duplicate entries. To prevent future occurrences, enable live migration. To do this, see Set up protection for live migration.