Problem
After changing the IP address of your staging server the cap deploy does not work any more and gives you the following error:

** [192.168.0.50 :: err] Host key verification failed.
** [192.168.0.50 :: err] fatal: The remote end hung up unexpectedly

Solution
You would need to login to your staging server (as your deployment user) and do an initial checkout for one time for the ssh keys to work.
So you could do something like the following:

$ ssh user_name@staging_server
$sh -c 'git clone -q git_user@192.168.0.50:repo_name /some/tmp/dir/temp_repo_name

Make sure that you reply ‘y’ to the question about the authenticity of the host as in:
The authenticity of host '192.168.0.50 (192.168.0.50)' can't be established.
RSA key fingerprint is xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xxb.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.0.50' (RSA) to the list of known hosts.

Next delete the newly created git project from your tmp directory, and then you should be able to use cap deploy as normal again from your development pc