Hi @Gavin Ross ,
1.According to my research on “Stalledduetotarget_mdbreplication”, this value is also returned from Data Guarantee API on checking the replication health of the target database copies if they are a member of DAG and have database copies. We might get this message if the MRS service is waiting to get this information from the target server about the replication status of the database copies. Please run the following commands to check the status of database copy and the status of replication.
Get-MailboxDatabaseCopyStatus -Identity <DAG> | Format-List
2.Please try to restart the mailbox replication service, then clear all move requests and create new move requests.
3.Please run the following command to modifying the priority to highest:
New-MoveRequest -Identity <> -TargetDatabase “DB Name” -BatchName <> -Priority Highest
For more information : Exchange 2016 Migration Status
4.In addition, based on the research of similar cases, I found that some users use the following methods to disable MRS Resource Health, after which they can successfully migrate their mailboxes. It should be noted that after modifying the registry, we need to restart the computer for the modification to take effect.
Regedit -->find the key "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchange ResourceHealth\MRS" --> set "MRS" REG_DWORD value from 1 to 0 --> Restart Exchange Mailbox Replication service
After migration is completed, we can revert back MRS value from 0 to 1 in regedit.
In order to prevent the impact of incorrect modification, you could also back up your Regedit in advance: How to back up and restore the registry in Windows
If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.