Cannot remove DAG member server or database copy

I am attempting to rebuild my DAG by removing the database copies and the availability group member servers.  I am getting errors that server01/mdb01 and server02/mdb01 cannot be found on the domain controller ad01 or ad02 (if i manually specify ad02). However when I check ADSI Edit it shows the mdb01 exists and has copies on server01 and server02 and that dag01 exists.

How can I resolve this without removing mdb01 via ADSI edit, I would rather not do this, despite having no user mailboxes the discovery search and arbitration mailboxes are on this database.  Below are my error outputs

This is my Exchange settings for the DAG  

RunspaceId                             : b904d45e-a217-48bb-8249-4e5d616c83af
Name                                   : ex-g4-dag01
Servers                                : {EX-G4-MBX02, EX-G4-MBX01}
WitnessServer                          : ex-g4-cas01.domain.local
WitnessDirectory                       : C:\DAGFileShareWitnesses\ex-g4-dag01.domain.local
AlternateWitnessServer                 : ad01.domain.local
AlternateWitnessDirectory              : C:\DAG Witness\ex-g4-dag01
NetworkCompression                     : InterSubnetOnly
NetworkEncryption                      : InterSubnetOnly
ManualDagNetworkConfiguration          : False
DatacenterActivationMode               : Off
StoppedMailboxServers                  : {}
StartedMailboxServers                  : {}
DatabaseAvailabilityGroupIpv4Addresses : {172.16.0.155}
DatabaseAvailabilityGroupIpAddresses   : {172.16.0.155}
AllowCrossSiteRpcClientAccess          : False
OperationalServers                     :
PrimaryActiveManager                   :
ServersInMaintenance                   :
ServersInDeferredRecovery              :
ThirdPartyReplication                  : Disabled
ReplicationPort                        : 64327
NetworkNames                           : {}
WitnessShareInUse                      :
DatabaseAvailabilityGroupConfiguration :
AutoDagSchemaVersion                   : 1.0
AutoDagDatabaseCopiesPerDatabase       : 1
AutoDagDatabaseCopiesPerVolume         : 1
AutoDagTotalNumberOfDatabases          : 0
AutoDagTotalNumberOfServers            : 0
AutoDagDatabasesRootFolderPath         : C:\ExchangeDatabases
AutoDagVolumesRootFolderPath           : C:\ExchangeVolumes
AutoDagAllServersInstalled             : False
AutoDagAutoReseedEnabled               : True
AutoDagDiskReclaimerEnabled            : True
ReplayLagManagerEnabled                : False
AdminDisplayName                       :
ExchangeVersion                        : 0.10 (14.0.100.0)
DistinguishedName                      : CN=ex-g4-dag01,CN=Database Availability Groups,CN=Exchange Administrative
                                         Group (FYDIBOHF23SPDLT),CN=Administrative
                                         Groups,CN=HostedExchange,CN=Microsoft
                                         Exchange,CN=Services,CN=Configuration,DC=domain,DC=local
Identity                               : ex-g4-dag01
Guid                                   : 5fa9b9fb-6397-4e9f-80e2-680902c78938
ObjectCategory                         : domain.local/Configuration/Schema/ms-Exch-MDB-Availability-Group
ObjectClass                            : {top, msExchMDBAvailabilityGroup}
WhenChanged                            : 2/11/2014 11:42:06 AM
WhenCreated                            : 1/27/2014 3:38:30 PM
WhenChangedUTC                         : 2/11/2014 7:42:06 PM
WhenCreatedUTC                         : 1/27/2014 11:38:30 PM
OrganizationId                         :
OriginatingServer                      : ad01.domain.local
IsValid                                : True
ObjectState                            : Unchanged

These are the error messages I see when trying to change DAG memerships and copies.  

[PS] C:\Program Files\Microsoft\Exchange Server\V15\scripts>Remove-MailboxDatabaseCopy -Identity ex-g4-mbx01\mdb01
The operation couldn't be performed because object 'ex-g4-mbx01\mdb01' couldn't be found on 'ad01.domain.local'.+ CategoryInfo          : NotSpecified: (:) [Remove-MailboxDatabaseCopy], ManagementObjectNotFoundException+ FullyQualifiedErrorId : [Server=EX-G4-MBX02,RequestId=759a6c79-b5cc-45e5-ba40-443ce1dd4c18,TimeStamp=2/11/2014 8
   :17:35 PM] 3175F3AB,Microsoft.Exchange.Management.SystemConfigurationTasks.RemoveMailboxDatabaseCopy+ PSComputerName        : ex-g4-cas02.domain.local

This is the general DAG screen showing the DAG status

[PS] C:\Program Files\Microsoft\Exchange Server\V15\scripts>Get-DatabaseAvailabilityGroup

Name             Member Servers                                      Operational Servers
----             --------------                                      -------------------
ex-g4-dag01      {EX-G4-MBX02, EX-G4-MBX01}

You can see from my ADSI that the mailbox does exist and has the mailbox database copies shown clearly.