Solution:
You do not create the accounts on the new server prior to migration.
Disable the firewall (CSF & LDF) on both servers.
On both servers, reset the r00t password to be 8 characters or fewer.
Change ssh config:
nano /etc/ssh/sshd_config
Set to:
PermitRootLogin yes
StrictModes no
Restart sshd:
service sshd restart
On the source server, set up the API key (CWP Settings > API Manager) for CWP Migration using the default CWP template.
On the receiving server, use the interface in User Accounts > CWP->CWP Migration.
After successfully migrating the accounts, revert all changes to your SSH configuration, reset the r00t passphrase to strong ones, and re-enable the firewalls.