Have you tried to restart the exchange server to test.
Exchange mailbox migration stalled.
Select migration migrate to exchange online.
A migration between exchange server and office 365 is considered completed after all the messages from the source mailbox are transferred to the destination mailbox.
Try using smaller batches.
On the select a migration type page select remote move migration as the migration type for a hybrid mailbox move.
Some stalled move request errors are straight forward and highlight an existing problem.
It can take a few minutes time for a coffee but check and the process should now have resumed copyingmessages.
The response time from the source is getting high and the migration batches are getting timed out.
This happens when the threshold for certain resources has been reached.
After we run this command we can see that the state is in fact queued and not syncing as per the above screen shot naughty microsoft.
Exchange 2016 we have cu8 in place utilizes throttling on move requests as well.
There comes a time where an exchange server has done it s time and a migration to a new server is in the pipeline.
Delete the migration task and recreate.
If you are reading this you have certainly noticed a stalled move request at times.
On the select the users page select the mailboxes you want to move to the cloud.
Restart the mailbox replication service.
But in some cases when the size of the mailbox is too large or the receiving office 365 mailbox does not have proper permissions then syncing is stalled and the migration will be stuck for an unlimited period.
In the top ribbon select admin and then select exchange.
Error solved mailbox export stalled due to source disk latency.
This delays the movement of the mailboxes.
Completing individual move requests from a migration batch.
It is called syncing and when the batch migration is in the final stages then it denotes its status as syncing.
The most recent stalled migration please note there are no errors on the migration job and no errors related to exchange server or the migration job in any event logs has the following message.
But the actual live mailbox remains on the source server until the process is successfully completed anyway.
To find out the actual state of the move we need to open up the ems exchange management shell and type the following command.
This might happen if there are any issues in the disk performance causing disk latency.
Small batch migration could be the best approach to deal in such situation.
On the enter on premises account credentials page.