Exchange 2013 to 2019 mailbox migration issue - StalledDueToTarget_MdbAvailability

I tried a MoveRequest again on Friday.

The report just has this repeated every three hours or so:
[EX01] The Microsoft Exchange Mailbox Replication service 'EX01' (15.2.1258.12 caps:3FFFFF) is examining the request.
[EX01] Connected to target mailbox '811ba64d-9bdf-4f72-b10d-8c203b0202d0 (Primary)', database 'MailboxDatabase01', Mailbox server 'EX01' Version 15.2 (Build 1258.0).
[EX01] Connected to source mailbox '811ba64d-9bdf-4f72-b10d-8c203b0202d0 (Primary)', database 'MailboxDatabase04', Mailbox server 'EX02' Version 15.0 (Build 1497.0), proxy server
'ex02' 15.0.1497.43 caps:0400001F7FFFFFCB07FFFF.
[EX01] Request processing continued, stage CreatingFolderHierarchy.
[EX01] Stage: CreatingFolderHierarchy. Percent complete: 10.
[EX01] Initializing folder hierarchy from mailbox '811ba64d-9bdf-4f72-b10d-8c203b0202d0 (Primary)': 218 folders total.
[EX01] Folder creation progress: 0 folders created in mailbox '811ba64d-9bdf-4f72-b10d-8c203b0202d0 (Primary)'.

It doesn't even have any stalled messages anymore. I really don't want to have to keep Exchange 2013 in place for one mailbox! Is there another way to try migrate?

EDIT: a colleague accidentally created a new mailbox on the old 2013 server.  I was able to successfully use new-moverequest to migrate it to one of the 2019 databases (although it was only 50MB).