zmztozmig FOSS 7.2 to NE 8.0.3 upload fails

[sononaco]

I am trying to migrate about 8 email accounts form a Zimbra open source server (7.2) to a Network Edition 8.0.3. I have provisioned the accounts with zmprov and am using zmztozmig to perform the migration.
The mailboxes download fine to the NE server and their sizes all match up as expected. However, they seem to be failing on the "upload" to the local server.
Some mailboxes have a few very old emails in them (like, 6-10 emails only) where there should be between 70 in one instance and a few thousand in another.
When working on a single mailbox, for example, I have noticed that it is a 12MB download which takes about 20 seconds. When it goes to "upload" it blazes through and all indications are that the transfer was a success.
Source and Target settings have been verified and nothing is showing in the FailedDirectory (but all accounts are in the SuccessDirectory).
I have tried it with resolve=reset and resolve=skip.
It is only a single domain which is listed in the Domains= line.
I have also tried it with and without DomainMap line (I have used DomainMap=domain.com domain.com)
Lastly, I have listed a few accounts, all accounts and one account in the Accounts= line (comma separated).
But for some reason the mailboxes are never uploaded.
I have the tgz files locally if that helps. I tried uploading them with this:
zmmailbox -v -u https://localhost:7071 -a [a valid admin account] -p [the password] -m user@domain.com postRestURL "//?fmt=tgz&resolve=reset" /tmp/ztozmig/clientdir/successes/user@domain.com.tgz
The above with localhost:7071 and the FQDN.
Running that I get this, regardless of account:
ERROR: service.FAILURE (system failure: POST failed, status=401 must authenticate)

com.zimbra.common.service.ServiceException: system failure: POST failed, status=401 must authenticate
I'm pretty much at a loss here. Any ideas?