Problem Moving Virtual server

We're having trouble moving a Virtual Server from one server to another.

There is an SSH key setup.

The remote SSH service is on a non-standard port.

Upon attempting to move the Virtual Server, we get the error:

Failed to update Virtualmin domains : The selected domains cannot be moved : A direct domain move from web1.domain.dk to web5.domain.dk is not possible, as VM2 cannot SSH without a password, or unless passwordless SSH between the systems is configured : Bad port '4975root@web5.redhost.dk' .

In the above, it looks like it may not be correctly applying the port to the SSH command.

Thanks!