This issue is added for information only - to enable it to be discovered

There is a short discussion here.

In summary, putting a job into the background does not detach it from the terminal process, therefore the SSH client is waiting for the background job to complete.
Ensure that STDIN/STDOUT/STDERR descriptors are closed (and reopened) in the process that you would like to keep running.
Use the daemon command in BSD or deamonize in GNU environments to simplify creating a stand alone process.